Donovan's goal gave the U.S a 1-0 victory over Algeria which sent them into the last 16 instead of on the plane back home.
"I've been through a lot in the past four years," said Donovan, who split up from his former wife, actress Bianca Kajlich, in July.
"I'm so glad it culminated this way. It makes me believe in good in the world," he said, crying and speaking so quietly he could hardly be heard.
The 28-year-old, who competed in the 2002 and 2006 World Cups, is one of the most skilful and exciting players in the U.S. but has not always lived up to expectations in major tournaments.
However, he came into this tournament after a strong showing at Premier League club Everton and has scored two crucial goals in South Africa - against Slovenia as the team fought back from two goals down and to qualify against Algeria.
LOWEST POINT
Donovan said his lowest professional point had come after the World Cup in 2006 when the U.S. failed to make it through to the second round and Donovan came in for much of the criticism following three below-par performances.
From a personal point, he said he had endured his hardest time in July of last year, without explaining further.
"Those experiences can harden you and can help you grow if you learn from them and if you look at it the right way," he said, as his coach Bob Bradley patted him on the shoulder.
"We will look back on it one day, a lot of us won't remember how it happened but the reality is we finished ahead of England in a World Cup group."
Bradley said Donovan had matured after accepting his role as a leader on the pitch.
"I think these kind of challenges came at a good time for him and he's never shied away from challenges," he said.
"There is a special feeling when you play on a team and you know people are really counting on you, when your character, your personality, is at the core of how that team does.
"Over these years, both on and off the field, he's grown and matured and accepted these kind of challenges and it's made a huge difference."
Asked what he saw when the ball came towards him in front of goal and with only two minutes left to run, Donovan said with a smile: "I saw a lot of things." Asked to elaborate he said "not yet".
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