When starting any new habit, routine or endeavor, it is smart to think about all the ways it could fail. I am not advocating a negative mindset here, but want you to be prepared for any bumps in the road that could result in failure to continue.
For example, think about your workouts. If you would like to workout consistently, great! Get started! But think about the things life is going to throw at you that might make it difficult. Plan what you will do when your child gets sick, or you get sick, or you forget your gym clothes, or you go on vacation. These are all roadblocks that could prevent you from staying in the exercise habit. Make sure you are prepared to handle any instance and stay on track.
Let's say you have been working out every Monday, Wednesday and Thursday evening at the gym after work. Then you get a new project and have to stay late Monday night, then again Wednesday night. If you haven't prepared for this, you might skip your workout since you are at work late and not work out all week. But if you have planned ahead for this possibility, and decided if ever something came up that you had to do during your regular workout time, you would switch to a morning workout using a dvd or online workout at home or replace a weekday workout with one on the weekend. No big deal, just switch to plan B and you keep your habit of exercise.
Preparing for any circumstance will help you keep on track. Failure is not an option!