The very best sportsmen are forced through physical and mental tests that would give us mere mortals nightmares.
But the consequence of those experiences can be a unique insight into sport and life in general.
In a new series, we talk to British sportsmen and women notorious for taking their sport, preparation and strategy to incredible levels.
Each of them has looked back on their career and identified the 10 key lessons their life in sport has taught them.
We also want to know the single most important thing you've learned from sport - follow the link to the 606 page to contribute.
To start us off: athletics legend Steve Backley.
1: Know your weaknesses - and do something about them
The best sportsmen I've met aren't necessarily fantastic at one particular part of the skill - they're just good at everything.
BACKLEY AT THE TOP
Broke world record three times
Only British track and field athlete to win medals at three Olympic Games
Awarded MBE in 1995 and OBE in 2003
I went to train with Olympic javelin champion Jan Zelezny in 1997, in many ways in search of the Holy Grail. I thought there would be something he was doing that would just be 'it' - the ultimate answer.
But if I found out anything, it was that he was good at everything. He didn't have a weakness, because he'd worked on them all.
Most of us tend to do what we're good at, because that's what we enjoy doing. What's actually more important is to find out what we're not good at, and then redress the balance.
2: Take your chances
In any sport, or in life, you have moments when an opportunity opens up in front of you. You have to be ready, and you have to grasp those chances with both hands.
At the 1994 European Championships in Helsinki, I wasn't expecting much - maybe just a medal if all went as well as possible.
But then I looked around after a couple of rounds of competition, and I could see that everyone was struggling. A window was opening.
And I thought, "Right - if you lot don't want it, then I'll have it - I'll drive harder than you, I'll give it a bigger shove." I ended up throwing about 85m, in quite tricky conditions - and winning it by three metres.
I remembered that moment for the rest of my career. So if you're thinking, "Should I do the race, or the competition, or play the match?" - well, throw yourself in, because you never know which opportunities might arise, and what might happen.
3: Be prepared
I used to write down a list of all the things that could go wrong.
People might think - hang on, that's too negative - you have to be positive. And you do. But by having that list, you find solutions to all your potential problems.
BACKLEY'S MEDAL HAUL
Four European and three Commonwealth golds
Two Olympic and one World silver
One Olympic bronze
What do you do if you're doing your shoes up in the Olympic stadium just before the final starts, and your lace breaks?
Solution: carry spare laces in your kit-bag. You could cross that one off the list.
I would spend two weeks coming up with a long list of everything that could possibly go wrong, work through them all and then end up with a long list of solutions.
You would then sit back and think - whatever happens, I've got a plan. And that was a great, great feeling.
4: Pressure can be your friend
People tend to view pressure as a bad thing, but it doesn't have to be.
For example, in a training session I'd be delighted to throw 80 or 82m. Three days later in a competition, I'd throw 90m. The pressure of competition was worth a good eight metres.
And if you want to escape from pressure, you can do - no matter how bad the situation might seem.
At my first Olympics, I was genuinely very, very scared. You've got a billion people watching round the planet, 100,000 in the stadium, the best athletes in the world all in one place - of course you're going to be scared. It's the natural reaction.
So what I did was to tell myself that I was simply doing an ordinary throwing session down my local track. That worked for me.
5: Have a goal
This sounds simple, but it's the first part of any journey - decide where you're going to. Only then do you think about how you're going to get there.
The outcome I wanted was to win whatever the major championship was that year - Europeans, Worlds or Olympics. I'd then ask what performance would help me achieve that outcome - invariably a throw of 88 or 89 metres would be enough to win.
Another medal to add to the collection
The next question would be: what's the process that'll bring about that performance? And that's where it starts to get really detailed - on your technique, the strength required, the power output you'll need, the nutritional plan.
All the time, you have to make sure you concentrate on the process, not the outcome - although all anyone will want to talk to you about is the outcome.
Your mates don't want to hear about how your point control is going - they want to know if you're going to win the Olympics, or throw a world record.
What's important is to be able to discuss that outcome with your family, your mates and people who want to glamorise the sport, but be able to focus on the process with your coach and yourself.
Because if you've done the planning right, the outcome should look after itself.
6: One man's sacrifice is another man's dream
The common perception of top sports people is that they have to make huge sacrifices to reach the top. But if you're in pursuit of your dreams, there aren't any sacrifices, because you're doing exactly what you want to do.
If your mates are going down the pub on a Friday night but you have to have an early night because you've got to be down the track early on Saturday morning, that's not a sacrifice.
I certainly never felt I was making a sacrifice, because I was doing exactly what I wanted to do.
And if there ever comes a point when you want to go down the pub, go down the pub - because if you resent what you're doing, then you're never going to have enough enthusiasm to do what you're meant to be doing anyway.
7: Believe in yourself
All great sportsmen have three things in common.
First, they all believe in themselves - neither a bad day nor a great day will affect their self-belief.
Second, they're highly motivated, always pushing hard for the next level.
Third, they're naturally talented.
You might think that last factor is the most important of the three, but I don't think it is.
If you look across all sports and ask yourself what their most successful performers have in common, they're all different shapes, different sizes and different personalities, but they all believe in themselves and they're all highly motivated.
8: Success and failure are not black and white concepts
At the Sydney Olympics in 2000, it seemed all set up for me.
Backley threw an Olympic record in Sydney - but took only silver
I'd gone bronze in Barcelona in 1992, silver in Atlanta in 1996, and I thought - Sydney, the new millennium - it's all there. It had been my dream to throw an Olympic record - and then in the final, I did.
But I still only came away with the silver, because Jan Zelezny went straight out and broke my new record by just 32 centimetres.
People say to me, "That must have been devastating." But sometimes you can't have any bearing on a result. For me it was all about whether you delivered or not - whether you did everything you planned to do and did as well as you could possibly do.
If you can say to yourself after a competition that you did - as I could after that final - then whether you came first or last doesn't really matter.
9: Keep changing - whether you win or lose
Successful sports people keep re-inventing themselves. Whether you win or lose, you always need to get up to a new level - and you can't do that if you're always doing the same old thing.
At the end of every season, I would make an assessment of how the season went. You'd then draw up a new plan, and work out what changes you had to make based on what went right and what went wrong.
For example, at the end of the 1997 season I decided to join the eastern European coaching system. By doing that, I learned a completely new way of doing things, and that gave me more armoury, more things to fall back on.
Get advice from other people. And be creative, particularly if you've been doing one thing for a long time.
By the time I finished athletics, we were doing all sort of weird and wonderful things in training, just to stay interested.
10: Don't get injured
It sounds obvious, but it's true: if you're injured, you can't win anything.
And injury isn't necessarily something that you have no control over - there are ways to make sure it doesn't happen to you.
Go to see a physiotherapist. Get them to assess your physical strengths and weaknesses. Then do the exercises that will protect the areas you'll stress doing your sport.
For me in the javelin, it was my shoulder, back and hips that I had to think about, so I had to made sure I did the 'prehab' to strengthen and protect those areas, and keep me healthy.