/lit/ - Literature

How do you prevent first person POV characters from coming across as annoying Gary Stus? I'm writing a novella from the perspective of a character who has delusions of grandeur but is actually pretty pathetic irl. I'm worried that I won't be able to carry across the "pathetic" part well enough and readers will think all the shit he says (including his ramblings on his barely coherent fringe ideologies) is meant to be taken at face value. Basically, I don't want to be like Patrick Rothfuss. Does anyone have any advice for me?