Start with projects that should be easy to commit to. Don’t start with projects of 3-6 months if you don’t have a strong track-record of one-month successes behind you.
Start becoming more sensitive about what you commit to. Be cautious about overcommitting.
If you need future flexibility, bake it into your initial commitment, don’t try to wiggle it in later.
Raise the bar on what counts as a valid excuse. View commitment as a long-term skill-building project.