Whatever 'brilliant' is supposed to mean, when I try to apply that adjective towards myself I'm immediately reminded about the numerous times I've felt humbled by someone else's infinitely higher brilliance (be it a book, source code, mathematical expression, song, poem, movie, etc) and then I just feel stupid for trying to place myself even close to those I so deeply respect.
Brilliant is impossible to be, what we can hope for is moments of 'brilliance', where one can come up with original solutions to problems. Ideas, revelations..
I do have those from time to time and it feels great.
But as a human being, it does matter what and how you feel in between those moments of brilliance.
And during a 'low' phase (which can last months, day after day), all your moments of brilliance are replaced with mental blocks, melancholy, cynicism and pessimism about everything and everyone.
It's a very bad place to be, it's painful, the feeling of being a fraud, the way you disappoint yourself and others by not following through, the way you see your dreams and hopes drown in a sea of confusion and frustration.
When everything you've earned/gained is slowly erased and you have to start again from step 1.
Yeah, I think that's a problem. You either kill yourself, drink/drug yourself to death or find a way to cope with it. My solution is to just obsess on books/studying new stuff when the mental winter comes and try to stay away from the easy escapes.