Germany goalkeeper Robert Enke, who committed suicide on Tuesday, had battled depression for six years.
Enke, 32, was struck by a train at a level crossing near his Hanover home. He had left a suicide note.
His widow Teresa said he lived in fear that their adopted daughter Leila would be removed from them if her husband's depression became public knowledge.
The couple adopted the eight-month-old in May having lost their biological daughter Lara in 2006 aged two.
Lara died of a rare heart condition, and Enke struggled to overcome his bereavement.
Teresa Enke said: "I tried to be there for him, said that football is not everything. There are many beautiful things in life. It is not hopeless.
Robert was a wonderful man, who had to cope with several blows of fate
Theo Swanziger, president of German football federation
"We had Lara, we have Leila. I always wanted to help him to get through it. He didn't want it to come out because of fear. He was scared of losing Leila."
Teresa and Enke's psychologist Dr Valentin Markser appeared at Hannover's AWD-Arena this afternoon to explain the background to his death.
Earlier, German journalist Alexander Bleick told BBC Radio 5 live: "Robert spent a long time with his wife in the hospital and [Lara's death] was a very sad moment for him.
"A year ago he and his wife adopted a little girl and everyone thought he would be fine again, but as far as we know he had suffered depression for a long time and was taken off training for several weeks in the past month at Hannover.
"Doctors worked with him to get his confidence back but it seems they didn't manage to do it."
Enke's agent said the player had committed suicide, and police spokesman Stefan Wittke, while declining to reveal where the note was found, said all evidence pointed to suicide.
"There is no evidence that would raise doubts about a suicide," Wittke said.
Police said the Hanover 96 captain's car, parked metres away from the tracks, was unlocked with his wallet still inside.
Born: 24/8/77, Jena, East Germany
Clubs: Carl Zeiss Jena, Borussia Monchengladbach, Benfica, Barcelona, Fenerbahce, Tenerife, Hannover 96
Germany debut: 27/3/07 versus Denmark Caps: 8
Awards: Bundesliga goalkeeper of the season 2008-09
Fans flocked to his club's Niedersachsen Stadium overnight to lay flowers and light candles at the gates in memory of their captain, who joined them in 2004. Hundreds more queued on Wednesday morning to sign an official book of condolence.
Hannover 96 removed all links to their regular website content, replacing them with a black page showing the simple words "Wir trauern um Robert Enke" ("We are mourning Robert Enke").
Germany's friendly against Chile on Saturday may be postponed. When asked about such a possibility, the general secretary of the German national federation, Wolfgang Niersbach, said: "It's hard to say anything at this point in time. We have to collect our thoughts. It's terrible, we are stunned."
Enke was not in the squad for the match, having recently recovered from a virus, but many expected him to be the number one goalkeeper for the 2010 World Cup.
The German Football League has announced a minute's silence will be held at grounds ahead of the next round of the top two divisions of the Bundesliga for the weekend of 21-22 November, with all players wearing black armbands.
Germany's 1974 World Cup winner Franz Beckenbauer told Bild newspaper: "I feel endless loss and sorrow. When you receive news such as this, all other problems seem small."
Theo Zwanziger, president of the national federation, said: "Robert was a wonderful man, who had to cope with several blows of fate."
Oliver Bierhoff, the German football team's general manager, said: "We are all shocked. We are lost for words."
Germany cancelled a planned training session and all interviews scheduled for Wednesday.
Enke started his career at Carl Zeiss Jena and club spokesman Andreas Trautmann said: "The right words don't exist for such a tragedy. We are shocked and our thoughts are with Robert's family. They have our heartfelt sympathies."
Jena, now in the German third division, will open a condolence book for Enke, with the intention that it will be passed on to his family.
The death caused shockwaves across Europe, at the various clubs where the goalkeeper had plied his trade.
Enke's former team-mate at Portuguese club Benfica, Nuno Gomes, told the club's website: "I find it hard to believe that he has died. It is a tremendous loss for world football, the loss of a man of rare qualities in our time. It is very sad news.
"I remember how he was just a young kid when he came here but, from day one, he made a great effort to learn our language and did it very quickly. He was a young kid with a huge desire to reach his goals and learn, a man with a capital M."
The club's current goalkeeper Moreira added: "I am shocked. All the memories I have are good ones. As a professional, he was one of the best to pass through Benfica and he learned to speak Portuguese in three months.
"If it was not for [Tuesday's] tragic accident, I'm sure he would have played in the World Cup."
The two Spanish clubs Enke played for, CD Tenerife and Barcelona, paid their condolences to his family.
Kevin Kuranyi, a striker for Schalke 04, told Bild: "It really can't and should not be true. Robert was such a great person. I don't know how I should tell my wife, she is good friends with Robert's wife. I feel for his family."
The German national federation posted a range of further tributes to the player:
• Christian Wulff (Prime Minister of Lower Saxony): "Germany loses an exceptional athlete and a very compassionate man. He was a role model."
• Michael Vesper (General Director of the National Olympic Committee): "I am shaken to the core. Our thoughts are with his family. This is a tragedy."
• Martin Kind (President of Hannover 96): "An absolute catastrophe, which I still cannot grasp."
• Ewald Lienen (former coach of Robert Enke with Hannover 96): "This loss is beyond words. I feel endless regret and sorrow that he was in such as situation that led to this final act."