Difficulty Committing to Myself

Over the past year or so I have noticed a change in my body. I am 30 now and while I am not overweight, I have definitely allowed myself to get out of shape. I have made several attempts to get on track with some sort of exercise routine that I enjoy and will do regularly...with less than stellar results. I will pick an activity and do it regularly for a while, then things come up, or I get home really late, or I feel unmotivated and allow that to win, and then pretty soon I am sitting on the couch again. I am making another attempt to get on track. I own two yoga DVDs that I have done in the past and really, truly do enjoy. The instructor lady on the programs is really positive and there are a variety of programs to choose from. So tonight when I got home I did yoga for a half hour. I really like it, it makes my body work and I can feel the working without it being painful. I am sweaty when I am done and I know that my muscles will feel worked tomorrow. I am in a good place right now and feel like I can commit to doing yoga a few times a week. I just have to maintain and keep it up. I am not sure where the problem comes up. I care about myself and my health and I want to be healthy and feel better about myself. I just need to work at honoring this promise to myself and do the best I can.