However, a new documentary about these resilient children, who refuse to surrender to a seemingly bleak fate, has changed everything.

When Tough Out was first screened in July at this year's FIRST International Film Festival in Xining, Qinghai province, it was met with overwhelming acclaim.

It is rated 8.7 out of a total 10 points on Douban, China's major film critic website, one of the highest score of all of the year's Chinese films. The film is to be publicly screened nationwide from Friday.

Over 60 children are now training at the resort in Tongzhou district in the east of Beijing, which was provided by an entrepreneur, and more philanthropists and companies have lent their support to the program. However, the production reminds Sun of the toughest time of his life.

"There is a world of difference between now and the beginning," Sun recalls. "Winning people's confidence was not easy."

The cost of the program's initial investment was borne personally by Sun and several of his friends. It was then, when he took the children under his wing to provide them with a seemingly utopian environment, that he began to feel the pressure of "raising a big family".

"I grew up in a family that was not very wealthy, and I was a very disobedient child," Sun says. "Baseball changed my personality, teaching me discipline and how to live life. Without it, I would have probably become a hooligan."