How Can I Keep My Word to Myself?

For me, confidence comes from doing what i say. When i say i'm going to do something, and then i get it done, no matter how i feel, i feel more confident in myself. So if i were looking at ok, how can i keep my word to myself? How can i build a character that makes me somebody who keeps my promises to myself? What will that look like? Well, to day, it means going to the gim at three 30, even though i'm really not in the mood too. Even though i'd love to just lay on the couch and watch t v, or, you know, take a few hours off before a webonar