How Long Can I Force Myself to Keep Coming to Work?

I am getting myself all worked up at work. I was going to say "for nothing", but that may or may not be true. I'm not sure I'm in a position to judge clearly. I feel completely and utterly useless. I have been sitting here trying to make work for myself. Every few minutes or so I try and convince myself that I should feel lucky since most people would kill to sit at work bored with nothing to do and get paid as much as I do. But personally, I just feel stupid.