The pals wrote and starred in 1997's critically-acclaimed Good Will Hunting, which won two Academy Awards.
Affleck's private life quickly became headline-making news because of his glamorous girlfriends, including Gwyneth Paltrow and Jennifer Lopez.
Affleck and Lopez went on to co-star in 2003 flop Gigli, and Affleck saw his popularity wain further after starring in badly-received movies Surviving Christmas and Jersey Girl.
The star subsequently turned his attention to moviemaking and directed 2007 hit Gone Baby Gone, which scooped the Hollywood Film Festival Award for Breakthrough Director of the Year.
And Damon has applauded his pal for his Hollywood comeback, which was cemented with last year's (10) crime drama The Town.
He tells CNN's Piers Morgan Tonight, "Ben kind of fell out of favour, he got just a crushing amount of publicity in his personal life and that made people, I think, loath to work for him a little while there, he was kind of in the penalty box.
"He did what we did originally did... Gone Baby Gone, his directorial debut... he wrote that directed it and then with The Town, he couldn't get a job as an actor that he wanted so he wrote it for himself and directed it."