I just don't know

The title says it all. I have no idea what to type, but I'm in a mood where I need to vent. The only issue is that I have no idea what needs to be vented. I just don't know... Have you ever had one of those days where you just felt like shit, and you didn't know why? Well, mine is almost like that. I know there are things that could make me feel like shit, but at the moment i'm not really thinking of anything in general. I'm just tired I guess. I just don't know...