It took me a while to actually get into a health and fitness routine that actually works. During my second and third years of uni, I went to the gym now and again, but every time I went, I would think - oh! I went to the gym! That means I get to eat more!
What I didn't do was the math. My BMR was 1700 cal. I was probably eating 2000-2500 per day.
Since December 2010, I've gone from a size 14-16 to a size 10. Lost 12kg, and feel better than ever. I go to the gym 3-5 times a week, plan my meals, enter my meals in MyFitnessPal, and have nothing off limits, I just fit whatever I'm craving into my calorie allowance.
It's changing the way you think. Listening to your body's internal signals (am I really hungry right now? No? OK, put down the chocolate!). I find having an organized life leads to a healthy body. If I haven't planned, then I'm just not healthy that week, and then I feel lethargic.
Also, finding an exercise routine that suits you, that you can fit into your schedule where you're not going to shrug it off and say 'I'll do it later'. Later is now. There is no later. I always go to the gym straight after work. Finding a workout that you find fun but challenging is also a must! You're not going to keep doing something that you hate. I love doing Les Mills BodyPump, and BodyAttack!
The main thing to remember is that it is hard, it does take work, but the benefits outweigh (excuse the pun) the costs. When you're healthy and fit, you feel happier, you feel more in control, and you feel like there is nothing you can't do.
Remember: 80% nutrition, 20% exercise.