Your brain is a problem solving computer. It's presented with patterns, some simple, some complex, and attempts to solve them. Your brain is a massively parallel problem solving computer. Some problems can't be solved. Some of those problems are minimal and are put aside. Some are less minimal and your brain continuously tries to solve them. This can happen consciously or unconsciously. Your genetics and environment may predispose you to treating minimal problems as more important than they are, and you can't get past them. So parts of your brain just get stuck looping through problem solving. Over and over. Your brain is a *biological* massively parallel problem solving computer. It runs on cells. Those cells require energy, those cells require resources. When a bunch of those cells get stuck looping, they burn too much of those resources. This causes dysfunction in other areas of the brain. This is clinical depression. How do you escape it? It's possible but difficult. It can be mitigated to a significant extent. Keep your nutrition up, don't skip meals, take supplements. Even plain old multivitamins will help. Meditation can help you find those loops and bring them to the front. If you can accept those problems, at least for now, you can possibly stop those loops.