Have you read much on decision making?

It's worth reading about the theory behind decision making as I think it makes decisions less stressful. Start by just reducing your decision space.

For example, if you go to a restaurant with a big menu decide beforehand that you will pick one of the first nine items on the menu. The square root of 9 is 3, so use the first three items as a gauge of interest. Starting from Item 4 pick the first item that sounds better than those first three items. Instead of choosing from a menu of 40 items, you are choosing from 6. Instead of committing to reading 40 items, you are committing to reading 4–9.

You can do the same throughout. Go on Google and open the first article on how to organize comics and pick the third organizational system and go with it. It doesn't really matter. You want to sell some? How many do you have? Take the first 20, and put them into 10 piles of 2 based on a quick rating of 1 to 10. Then just pile the rest on (or whatever way protects the books). Each set of 20 needs to be separated out like that. Commit to selling 10% or 30%, and just pick the 1 or 1/2/3 piles. It's fine. You are successful and could rebuy one you regret, but you probably won't.