The Irish actor admitted he wasn't worried about losing friends after giving up his boozing sessions and 60-a-day cigarette habit.
According to Scottish newspaper the Daily Record, Colin said: 'I didn't lose any friends because of it because it doesn't bother me watching my mates getting drunk when we go out.
'But it was the best decision I ever made in my whole life. Now I go home at 1am instead of four in the morning.'
The 34-year-old has now swapped drink for the gym for his role in a remake of Total Recall.
He said: 'I've got this hairy Croatian boxing coach who tortures me every day.
'I need big muscles for this new movie. He's killing me with his drills.'