It's called discipline. I've said it before, I'll say it again: I'm sure many of us would rather be doing something else with our time than working out. There are days I know I'd rather be lazy and sit in front of the TV. But, I get my butt up and go to the gym. Once I'm there it all kicks in.
It's a bit like brushing your teeth. You need to just work it into a regular schedule.
If you're happy with the way you look (only you can judge), then fine. But if you really want an improvement, you need to get to the gym and work out regularly. The same motivation that works for me may not work for you. You have to figure out what will get your ass in gear and use that.