The Irish star took full advantage of his newfound fame after his breakthrough role in the 2002 sci-fi hit Minority Report, and he fell into a downward spiral of substance abuse.
He entered rehab in 2005 for addiction to prescription and recreational drugs and quit drinking upon his release in 2006, and has since learned to embrace the "sweet simplicity" of his healthy lifestyle.
And Farrell, who will next appear in the Total Recall remake, insists he is lucky to still have a career after behaving so badly in his darkest moments.
The father-of-two tells Britain's Men's Health magazine, "I had burned so many bridges in the film industry that I couldn't get a f**king meeting. But now I'm just enjoying life...
"One of the big things that I was drawn to about drugs was the ritual. I don't put the same level of energy into healthy living as I did into unhealthy living, but I eat really well, drink loads of green tea, and take a s**t load of vitamins. It's so f**king boring... life has mutated to take on this sweet simplicity that I am really f**king OK with."