The moment you start avoiding action again, due to fear or aversion, you are re-entering a nonproductive phase. 

It comes from a misapprehension of what it will actually be like to do the work. 

The moment you start acting on something, you are at the beginning of the end of the anxiety associated with that thing.

What seems like a tangled cloud of open-ended old to-dos is actually a series of independent happenings, which are best treated individually.