The parents of Madeleine McCann have said their trip around Europe to raise awareness of their missing daughter is their way of taking positive action.
Madeleine McCann has now been missing for more than a month
Gerry McCann said that if the couple had simply "stayed indoors" then they would "be shells of the people we are".
Mr McCann was speaking in Berlin, where he and his wife Kate are seeking information about the four-year-old abducted in the Algarve 34 days ago.
Earlier Mr McCann said Madeleine is "more likely" to be alive than dead.
The couple have already been to Rome to speak with the Pope about their daughter.
"If we had, for example, stayed indoors, locked ourselves away and waited, and waited, and waited, for a month, we would be shells of the people we are," said Mr McCann.
"I can understand why people are amazed at what Kate and I are doing. Before this happened to us, we would have been amazed.
"I am sure everyone in this room has asked themselves how, when our daughter whom we love so much is missing, can we continue to function?
"In the first two or three days we were almost non-functional and one of the worst feelings of all - along with the terror, the anguish and the despair - was helplessness."
Earlier Mr McCann said that the couple were sure Madeleine is still alive.
"There is an absence of evidence to the contrary," he said.
During one of Wednesday's press conferences, Sabina Mueller from German Radio asked how the couple felt about the fact that "more and more people seem to be pointing the finger at you, saying the way you behave is not the way people would normally behave when their child is abducted and they seem to imply that you might have something to do with it".
Mrs McCann replied: "To be honest, I don't actually think that is the case. I think that is a very small minority of people that are criticising us.
"I have never heard before that anyone considers us suspects in this and the Portuguese police certainly don't.
Mr McCann said: "Without going into too much detail, we were with a large group of people, and you know there is absolutely no way Kate and I are involved in this abduction."
During the conference Mrs McCann also said that the trips around Europe were "not easy".
She said: "A day like today is very intense but it is actually just one day. We do have a lot of time back with the children, Sean and Amelie.
"We are doing this for a purpose, to try and find our daughter and to try and get Madeleine back - that is very important to us and Madeleine."
The couple are spending less than 24 hours in Germany before flying to the Netherlands, where they lived in 2004. They flew to the German capital on a private jet on Tuesday night.
The couple were also featured in an appeal for information on BBC One's Crimewatch.
It is thought Madeleine was snatched from the family's apartment in Praia da Luz on 3 May while her parents were at a nearby restaurant.
Portugal is a popular destination for German tourists, and the couple hope someone may have some useful information which could help the police investigation.
Mrs McCann, wearing green and yellow ribbons tied to her waist, said: "There has been a lot of speculation and it is hard not to think the worst.
"But as time goes on and there still isn't any news, we have to think positively."
Mrs McCann dismissed criticism the couple were courting too much publicity in the search for their daughter.
"We have got to feel happy that we have done absolutely everything we can to get our daughter back - I don't think any parent would be critical of that."
During their visit to Berlin, Mr and Mrs McCann will meet British ambassador Sir Peter Torry, Germany's Deputy Justice Minister Lutz Diwell and the colourful Mayor of Berlin, Klaus Wowereit.
They then go straight on to Amsterdam where the couple lived in 2004, leaving when Madeleine was just a year old and Mrs McCann was pregnant with twins Sean and Amelie, who are now two.
This will be the first time they have gone back and they expect it to be a highly emotional visit.
Friends in the Netherlands have been working behind the scenes since Madeleine was taken and 500 billboards bearing her face are being put together ahead of the trip.
After further interviews on Wednesday, they will fly back to the Algarve in time for a jazz concert in their daughter's name in Lagos.
The couple left Sean and Amelie at the family's holiday apartment in Portugal with Mr McCann's sister Trish Cameron and her husband Sandy.
The McCanns hold up a set of pink pyjamas in the broadcast
In the Crimewatch appeal, Mrs McCann, 38, held up a light-pink pyjama top with capped sleeves and a picture on it of the cartoon character Eeyore, who is curled up with the words "Sleepy Eeyore" written underneath.
She also produced white cotton pyjama bottoms, covered with small flowers and carrying another Eeyore motif on the right leg.
The pyjamas are identical to those Madeleine was wearing when she disappeared and belong to Amelie.
Mr McCann, who turned 39 on Tuesday, gave a detailed description of a suspect seen carrying what was thought to be a child on the night Madeleine disappeared.
He said the man was approximately 35 years old, about 5ft 8in or 5ft 9in tall and had dark hair, which was parted at the side and slightly longer at the back.
He said the man was wearing a dark jacket slightly longer than a suit, beige trousers and dark shoes.
Asked if he thought the man had taken Madeleine, he said they were: "suspicious of the timing and that person needs to be eliminated from the investigation".
He also urged people to hand in any pictures taken around the time Madeleine vanished at Praia da Luz with strangers in the background.
The McCanns are also expected to make a trip to Morocco, a country which has been linked to the case because of a reported sighting of Madeleine there.