The answer to the question of what is easier -- to start or to keep going -- is it depends! It depends because the answer relies on the person who is in question. Some people, like me, find it harder to start but when I get going I tend to keep on going. But for others, they might it find it easy to start but rarely do they finish the job. So each person must work out his or her own challenges and that is wh you can't have other people run your life but you must make it your own, and hopefully in the process, assist others along the way.
Keeping promises is hard. It requires us to do things we don't want to do. But keep those promises you must do. Otherwise, do not make them in the first place. But since you have made them, you must keep them, especially if it would benefit all those involved including yourself.