Hollywood actor Robert Downey Jr is convinced cleaning up his life will be the hardest thing he's ever done - because normality terrifies him.

The reformed hellraiser, who has battled alcohol and drug addictions for most of his adult life, is petrified by the thought of leading a quiet life.

He says, "The idea of having mastered my own life (scares me).

"I also think commitment is really scary as I'm a bit of an escape artist.

"To trust somebody is terrifying. I wonder if I'm more afraid of harmony than discord, as clearly I haven't had trouble with things being chaotic in the past."