“I’m afraid I’m going to let you down”

My bf said “My biggest fear is that I’m going to let you down”

I asked, like what, how, lol cheat on me or something?

He said “maybe. I don’t want to and I’ll try not to though”

We got into a huge argument after as I tried to understand what he meant by that. Obviously the convo went no where as all last night I played this conversation in my head trying to understand. Please, besides him meaning he will possibly cheat on me, could there be any other explanation or perspective I’m missing. Please be kind, I know most people would just leave if their bf said this