When I say I'm going to do something, and it does not get done, it's because I'm unwilling to do it, or because I have accorded it a low priority.
There is no such thing as forgetting to do it, losing track, etc., since prioritising something entails ensuring there is a system for making sure the task gets done instead of relying on thoughts occurring to me spontaneously to remind me. Committing an important item to memory and hoping it will return to me later on (when I am aware I have forgotten things in the past) is one way of according something a low priority.
The same applies to any other apparently involuntary or extraneous reason for not doing something.
Unless the real cause of the failure is identified, the problem will not be solved, and the failures will recur.