Every so often James Cracknell is hit by a wave of doubt and wonders 'what the hell am I doing?'.
The double Olympic gold medallist has good reason to worry. On Saturday he flies to the Canary Islands to row across the Atlantic Ocean, accompanied by the BBC's Ben Fogle, who he describes with a grin as a "poor rower".
"He's probably not going to be our next Olympic champion," Cracknell told BBC Sport. "For one he's too short! But that said, he brings strengths I lack on a monumental scale."
Ben's positivity will hopefully off-set my negativity
Their pairing is something of an odd couple. They admit they still don't really know each other and the idea was spawned after a brief chat over drinks.
"I was at this party and got talking to Ben," Cracknell recalled. "He told me we should do the Atlantic Rowing Race. My response was 'no way'. But days later I couldn't get it out of my head.
"So I eventually told my wife it was something I had to do. I don't think she was happy initially and I'm sure she's pretty nervous.
"Added to that, she's left completely in the lurch with the kids and I'll be missing Christmas. But she knows I have to feed my competitive urge and I think she's proud of what I'm doing - well, that's what I keep telling myself anyway."
Cracknell and Fogle have only got to know each other in the last five or six weeks, through training sessions and endless phone calls to organise their bid, which sees them take on 27 other teams from 27 November.
Already their team work has paid off. They have covered their costs for the bid, plan to raise money for Children in Need and are "physically, if not mentally" prepared to board their boat - the Spirit of EDF Energy.
The boat will be rowed for 24 hours a day, they will row in shifts of two hours on and two hours off, and hope to complete the crossing in 50 days.
ROWING THE ATLANTIC
Boat: The Spirit of EDF Energy, with a cabin for the pair to sleep in
Goal: To row 24 hours a day from Canary Islands to Antigua doing two hours on each and two hours off
Food: Mostly rehydration products, three portions of granola per day, peanuts and biscuits
Drink: A desalinator on their boat converts five litres of sea water to drinking water per day
Daily calory output: Up to 10,000 each per day
Back-up: Global positioning system to guide them across the Atlantic
Despite Fogle not exactly being the next Matthew Pinsent, Cracknell added: "He's a really focused, competitive guy, and is far better on the navigational side than me - he's certainly had more experience on the ocean.
"Also, he's so positive, which is just what we need on those particularly low days when we're struggling and possibly haven't talked for days.
"His positivity will hopefully off-set my negativity. I can be a bit of a grump sometimes but I'm incredibly driven. I'm confident we'll just keep going."
Cracknell's competitive edge has already brought him two Olympic golds and may yet provide him with a third in Beijing.
For now, he's making no promises and plans to decide his future in January.
"I got back in action with three guys the other day. Admittedly they were all fully fit and had to carry me but I loved it," he confessed.
"But I've set January for my decision, which is when I will have just finished this expedition. Having rowed for 50 days it'll probably be the last thing I'll want to do!"
To prepare, he and Fogle have been training with the SAS as well as talking to teams who have previously tackled the Atlantic row.
Some have been helpful, Cracknell concedes, but most have not helped his state of anxiety.
"Some of the stories sound woeful," he said, "but I've got a clear favourite. We were told in the last few days to the finish in Antigua, you are accompanied by a dozen sharks.
"In some respects, we'll be like, 'let's not mess up', and in others we'll be like, 'wow, that's awesome'."
Despite his habitually cheerful outlook, Cracknell is well aware of the dangers the trip entails.
"In the past if I've cracked in a boat, it's cost us a race," he said. "If things go wrong out on the Atlantic it's a lot more serious."