[CalRobert]

Well, you can change your own environment. This is personal, but what has worked has been one of:

* Have a gym close to work (i.e. 5 minute walk or less) and a corporate culture that lets you take 45-60 minute lunch breaks. Bonus - I find this makes my afternoons much more productive.

* Live 6+ cycle-able miles from work and ideally have a shower at work

* Be a student with a gym near your classes and an hour or two to kill between them

When one of these things is true I always manage to get a decent routine going. Without that I have always failed. Moving away from southern California to a place where I walk and cycle everywhere has helped.