Boateng blames his wild lifestyle and lack of support at Spurs for failing to reach his potential as a player.
The midfielder went to Portsmouth from Tottenham before settling at AC Milan in 2010.
"Tottenham didn't give me a chance and I didn't focus on work. But those problems helped me become a better player and man," Boateng said.
"I was on a downer because I wasn't playing and I was going out late to nightclubs.
"I looked in the mirror and said 'What do you want? You want to go out every night with your friends? What is more important?' I answered 'I want to be a big player.'"
Boateng will face his former North London rivals Arsenal in the Champions League this week.