When is it fretting, and when is it procrastination?QUOTE]
I'm not ENTP, but I understand it like this: fretting comes out of a sense of uncertainty, procrastination comes out of lack of will/drive/desire/interest/need.
Generally, when there's a fail to implement on my part, it tends to be for one of two reasons. Either I'm thinking so much because I'm not confident I completely understand the situation and, therefore, I'm not really sure what course of action to take and the risks (in my mind) are just too great to do anything but pull the covers over my head and think some more. Or I've exhausted so much energy in formulating the idea, defining all the intricate details and planning each little step that I actually feel like I've done it already and I really don't want to 'do' it all over again by actually doing it for real... so I go do something else instead.
I think the situation and sometimes even the subject material itself will determine whether or not it's binary variable, more so than strictly ENTP or INFJ (if that's what you're meaning?) Just from what you've mentioned in your post, I can see different 'stakes' in each situation. I guess in the most basic of situations, you might enjoy crafting and formulating the idea so much so that the idea itself is the point of crafting and formulating the idea in the first place. If this is the case, it would only be natural for you to not execute when you're operating purely from that position. But things would get a little murkier when that simple pleasure is not the only factor at play in you. And if 'doing' is something that's not natural to you (in the respect that it's not necessarily a given - not everyone thinks for the pure pleasure of thinking!) It would make sense to me that you might fuss a lot in certain situations and even end up overwhelmed by your own ideas at times.
So, to me, it's not as simple as ENTP's are procrastinators or INFJ's are over-analysers (not that anyone here is actually saying that, but I hope you get what I mean anyway). It's more about what a person is trying to achieve in a specific situation and how their natural tendencies aid/impede them.