Distractions are definitely caused by internal triggers and sometimes there is no perfect way to deal with them.

I'm adding features to an existing service, and it causes me emotional distress, because there are 3 layers of legacy code next to the stuff I'm adding. I so want to go hog wild and rip up the old stuff. The only problem being, we're short on time and devs right now, so I have to add these strategic features.

Here's how I deal with it: Chunk up the work, and think of the next small piece I can accomplish. Get started on something, and leave the last easy piece sitting there while I take a break. When I come back and finish that chunk I have a positive reward feeling for finishing a chunk of code. Then I feel more like starting the next piece.