This is sound advice. I was once recommended something similar: budget time to do <something you don't want to>, and then do NOT invest more time than this. Stop once you reach the timebox, even if you feel like you want to continue working on it. Because you have to learn to decouple this task from your motivation. You are not doing it because you feel like it, but because you decided to do it.
You're looking for a feeling of excitement, to really feel alive.
After the initial rush, that feeling fades. So do your chances of finishing the project.
Recognize that rush/excitement/feeling alive WILL NOT come from your project.
Disassociate that feeling from the project.
Then you'll pick projects far more stingily.
And then you'll finish one of those projects.