I sometimes wonder if a similar mechanism might be at play when you imagine accomplishing your goal in a Walter Mitty sort of way.
There are many projects which I can envision completing, and which I know I have the technical skills for. But I gain a certain amount of satisfaction just from picturing the completed work, and in the end I don't actually put in the effort to make it reality.
I suffer from the same affliction. Daydreaming forward often reveals additional functionalities and synergies and implications, so it even "feels" like progress, but I've learned the hard way that skipping to the last page of the book is counter-productive.
I vaguely remember something about research showing that visualisation works well if you visualize both the positive outcome of achieving a goal and the negative outcome of not achieving it.
There are many projects which I can envision completing, and which I know I have the technical skills for. But I gain a certain amount of satisfaction just from picturing the completed work, and in the end I don't actually put in the effort to make it reality.