As bad as yesterday seems to be, today is a new day and so will be tomorrow. Thus remember that whenever you feel you are losing hope it must be put into perspective. What you lose is only that day's experience. The next day is still very much in the working and a clean slate.
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.