Practice the first step until you master it before moving on to the next. For someone who is not currently exercising, walking to class instead of taking the T may be a more realistic and an attainable first step towards implementing a regular exercise program than working out for an hour every day. In making any kind of change, you may have times when you will go back to the old way of doing things. Change is a process, and a lapse does not mean that you have failed or that you will have to start over from the beginning. It is important to go right back to the step you had been working on and to try again.
Persistence is one of the most key elements of success.