My last campaign that failed was because I thought I could handle GMing twice a week for two different games. Both D&D 5e with one set in a homebrew points of light style setting and the other set in Ravnica. Pretty quickly I found that I only really have enough creative energy for one thing at a time. I would be really excited for one while forcing myself to run the other. Funny thing is it would switch every so often which one I was enjoying. Eventually I laid the Ravnica game to rest as it was the newer of the two and I had some big ideas on taking the party to the Shadowfell for the other.