Well, I think that an appropriate second post should revolve around motivation. What keeps people working out or eating healthy when it's so easy to sit on your butt all day and eat junk? I don't know about most people, but I'll talk about what keeps me going (and how I've fallen off the wagon in the past).
Social obligations - I mentioned before that I began running to help motivate my husband. This is probably one of the most powerful motivators out there, and it works really well for me. If you have a social obligation to continue working out or eating well, then it's easier to move past the days that you just don't really care about working on yourself. I've been able to transition this from helping my husband to helping myself and my friends by agreeing to meet at local 5k races. We meet about once a month at these races and have a blast. You are probably thinking "you mean you pay people so that you can run?". Well, yes. I know running is a free sport, but paying $15-$20 a month for a race that helps keep you motivated and competing with yourself is really worth it. Plus, it's still cheaper than a gym membership!
Competition - I actually try to avoid competing with others in terms how fast or far I can run. However, I do compete with myself. If you focus too much on how others are doing better than you are, then you're only setting yourself up for failure. I know I will probably never run a 5k in under 20 minutes, but that's okay. As long as I have some improvements each time I run in a race, then I'm okay. I realistically only expect an improvement of about 1-2 minutes per race (i.e. if my last race time was 40:30, then I would be really happy if I can break 40 minutes). If I don't have any improvement, that's okay too. I'm looking for an overall improvement in my fitness and quality of life. So far I've been feeling better about myself because I have more energy and less stress.
Stress relief - Ironically this is one my biggest obstacles. Sometimes I have so much stress going on that I don't feel like taking the time to work out. It's amazing how quickly all of that stress can melt away once you get past the first mile when you're running. By the end of the run, the endorphins have really kicked in so the stress gone.
Training log - It's as simple as writing down when you worked out and for how long with some notes on how you felt. This not only keeps your spirits up, but you have proof of your progress right there in your hands.
I've not always been the most consistent runner out there (notice I started running nearly 2 years ago but only started becoming consistent 6 months ago), but try these tips and see if they help you stay on track. They've worked really well for me and I'm sure that in some fashion they'll work for you.