I had to take a day off today, because I came to the realization that I suck at my job. It's not particularly difficult, it's just the level of attention needed to fulfill the duties expected of me is something I am not capable of doing.
I've been there for about 5 months now, and there are still too many things I don't know, too many things that I tend to overlook.
This could be a case of me having way too high of expectations of myself, but I feel I should be doing better. It's just frustrating.