It's more than just doing what you say you're going to do when you say you're going to do it, it means continuing to do the things that lead up to you making that promise. There are days that don't fit well into the master plan, but those are the times that you show it the most and follow through on something that you may have no interest in doing at the time.
We all get sidetracked; that's life, but when other people start depending on you to hold up your end of the bargain, it's bigger than you, and your lack of commitment could be the lynchpin in the entire process. It may also be the difference in your success or failure. Better yet, it could be the difference in someone else's success or failure that follows your example.
How bad do you want it? You may not want the responsibility, but do you want to let the person or people down that you have asked to depend on you? They may forgive one time, but they won't trust you to do what you have promised if you let it slip more often, or if you continue to declare your commitment only to fall off again. At that point, you are just crying wolf and although people may sympathize or even empathize with your situation, they will look else where.
I was once told the story of the Chicken and the Pig about breakfast. It was more of a question, but it simply asked what was the difference in the two. The answer is that the chicken was involved, the pig is committed. A ham and egg breakfast, or one with sausage or bacon still has the chicken providing part of it with next to no effort, but the pig gave everything.
I'm not morbid enough to think I have to sacrifice myself to be successful, but I do have to sacrifice parts of myself to make that happen, and it may be parts I'm uncomfortable losing. I have ben fortunate enough to be able to start over and have a second career, have good friends, and my father taught me a great deal of respect for others, but at some point or other all of those things have required some level of sacrifice. It's not convenient, and there are a lot of things that may have been more fun to do along the way, but any way this is drawn up, it will take an all or nothing approach. I hope I'm up for the challenge.