habit forming

For most people, the concept of having a "habit" is a bad thing, something that people want to break. But right now, I'm really struggling with devloping some habits - good habits. It may sound weird, but trying to start a habit is a whole lot harder than trying to break them. I used to have a consistent habit of exercising four mornings a week, and at one point in my life, I had a consistent habit of praying and spending time in the Word. At this point in my life, I have neither. I've struggles for about a year with the exercise habit, and as I think about it, my prayer time also dropped off about the same time. I'm not sure what the connection is, but as I think about it, the time link does strike me as odd.
How do you develop a habit? I've read that habits can be formed in about two to three weeks, but up to that point, it's like pulling teeth.