Generally, people don't train in themselves the habits, self-knowledge and control structures to ensure they act on their plans and goals.
You can be better at committing to things by practice, but commitment cannot be practiced on its own. It must be practiced in conjunction with some other goal.
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Any goal or project will usually have these basic qualities:
A goal is then a group of different features that get bundled together. Some are necessary, others are optional, and some are better to postpone.