"Don't think" is the wrong advice. There are two problems to thinking too long. If the initial thought is wrong, all follow-up reading and consideration will be wrong. Garbage in, Garbage out. Indecision in Go seems to stem from knowing the proper move without knowing why. If you don't know why a move is good, you cannot evaluate it during a game to see if it works in a specific position in a game, like Joseki Poisoning.

If you want to really teach a beginner that appears to think to much, Fix the weakest link. That is, fix the start of their thought process. I.e. How to look for urgent moves first. Once you've done that, encourage their reading abilities so that they can follow through on their thoughts, reducing indecision. Perhaps we should say: Don't think, read!