Re:Steve-O - Demise & Rise
I think having an addictive personality can come into play, and i know i have one. Getting up an two hours early to go to the gym if i know i cant make it later on and being unreasonably pissed of if i cant make it, spending my spare time reading and learning about training and nutrition, always having the thought of needing to feed in the back of my mind, ignoring bills to pay for extra food and other things. But of course there are 'normal people' who just train and participate in activities for the love of it.
For me having an addictive personality, training keeps me clean and sober, and makes me a better person.