Along the way, he has developed an appreciation for looking after his own mental health and now reflects on his journey, and the lessons he's able to pass on to those experiencing times of struggle.
"As you grow older you learn to just be comfortable in your own skin," . "Any advice I can give to any young player or any person, is to just be comfortable in your own skin. Everybody makes mistakes.
"When I was younger I used to get this real anxiety, where I'd know somebody and I would be chatting freely with them, and then I'd walk away, and something would pop into my head and it would make me feel anxious. And I literally couldn't talk to that person that I'd just had a conversation with! It was nerves, crazy nerves... pure self-doubt."
That doubt intensified at United, where Sir Alex Ferguson saw something in him and yet that faith was not enough to rid Foster of his inner struggles, proof that sportspeople are no less prone than the rest of society when it comes to dealing with pressure.
Mistakes in the 2009 Community Shield and high-profile clashes with Arsenal and Manchester City made for a nightmare start after a long wait to replace Edwin van der Sar. Within months, his chance to establish himself at arguably the most recognisable club in the world was over, a dizzying and damaging run affecting his form and confidence.
Foster, who went to the 2014 World Cup and has eight England caps, blames social media for its role in placing pressures on young people - inside and outside of sport - as they grow up in a world where interaction with people they do not know and have never met becomes commonplace, something he sees inside the Watford dressing room.
"Kids nowadays, they live their life on social media. It's not real - it's complete crap. We'll finish a game, no joke, the second they (young professionals) do they'll pick their phone up, and they're straight on twitter. They're not looking at messages from their friends and family, they're looking at people they've never met before, and that will have a bigger bearing on their mood than the people that actually matter.
"In the age of Instagram and twitter, where people just show off 24/7... it's an absolute devil. For young people who don't know how to use it in a good way, it can be a problem.
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