I seem to have quite an addicitve personality. For example, giving up smoking years ago was extremely difficult for me (but well worth the effort). These days, keeping fit has become a bit of an addiction which partly offsets my love for food and a few scoops of Guinness. Whilst I started to exercise to keep fit phyically, for me the obsession to do exercise a few times a week now comes from how good it makes me feel mentally; in particular, how much better I cope with stress. I can have the world on my shoulders thinking about another week in the office, but after a good cycle, run or whatever I'm ready to face anything.
Whilst anything has to be kept to sensible limits, by channelling an addictive tendency towards something like cycling is obviously a great counter for other temptations which take life down a not so healthy path.
After cycling or the gym every morning this week, I'm now off for a well earned steak and a pint (or 2!) of the dark stuff