How can i get the willpower to stick with exercise to lose weight?

I'm in my late 20's, 5 foot tall and am slightly overweight. I gave up smoking after 13 years, it took about a decade to get the willpower to finally quit (has now been nearly two years). Unfortunately i put on 21lb in weight after i gave up. I have managed to lose just 5lb. I now weight 9st 9lb (135lb), i'd like to get down to 8st 7lb (119lb), I would like some advice on how to get the willpower to stick with an exercise and healthy eating plan, i don't want it to take me a decade to get the willpower for this (imagine how big i could be by then)?!, Has anyone been in my situation and overcome it? How did you get motivated? Any advice would be greatly appreciated. (I'm not interested in slimming pills or starving myself,just a healthy lifestyle i can mantain and stick to)

Don't look at it as 'going on a diet'. Look at it as a lifestyle plan; it's how you should eat the rest of your life.

Good job on quitting smoking.

Motivation? Maybe put notes around where you'll see them; on your dresser, refrig, etc.