I would have to agree with Rockbiter that it's a lifestyle change. I couldn't stick to the gym before because those other times I viewed it as a chore I do to get in better shape, so I lost motivation quickly if I didn't see results.
Once I started to look at it as something I enjoy, everything else start to click. I start to research on diet and eat a lot more (4000 cal/day), go to the gym regularly, scheduling my time around to make room for the gym instead of the other way around, spending more time outdoors and staying active, etc.
I still only can keep up with my 4-5 days/wk workout, 4000 cal/day diet for 2-3 months at a time (it's HARD). But I try to stay active during the 1-2 month break: swimming, hiking, yoga, etc., and go the gym at least 2x/wk during breaks.
Never feel better about myself. Sometimes I do fall off the wagon and lose some muscle mass as a result, but that actually just give me a kick in the ass to work harder again.
It's a big lifestyle change for some and it might take a few tries. Not to say one has to become a gym rat and revolve your entire life around it, but you do have to make health and fitness a priority.
And like Rockbiter said, try pick up some other activities as well so when you get burn out form the gym, you can dial down your gym time and do something else and stay active.