This is something all DMs should read, in case they are in a similar situation. If any of this sounds familiar, it's time to quit.

I'm a fairly typical DM. The people I play with are friends I've had for some time, and we use D&D as an excuse to get together. Out of the group, about half have read the core books, and only one other person actually managed to understand what he read.

It would usually be either me or that person who would DM. Some other players would try their hand, but only us two were able to run anything longer than a one shot adventure. So, we had a friendly competition going, each of us trying to prove that we were the better DM. We each had our strengths and weaknesses, and we actually worked hard to become better at DMing. Experimenting with different things, cutting apart premade adventures to understand the underlying mechanics and thematics, and putting many hours into our own adventures.

When he decided to transfer to a distant college, I became the lone DM. Once again, people would try their hands at it, but 95% of the time I was DMing. This was alright, until some strange, indefinite point.