JesserGood morning, Jesser.
I actually have more trouble with the spartan quality of this dream, than I do with the extremely detailed and long ones.
The stark color scheme intrigues me. On a white background, you run with a black cat, while bleeding red. In a way, this reminds me of the old chestnut, "what's black and white and red all over?" The answer being: a newspaper. If this dream referred to writing in some way, I wouldn't be surprised.
Black cats have occult connotations - whether they are good luck or bad luck is up to you.
If you're running with no clear destination in mind, perhaps you are running from something instead of to? The cat seems to know where you are going - perhaps the cat represents your instincts here. It can also be a totem for you - a representation of your inner beast, which tells a bit about your own personality merely by the form it takes. If you identify with the cat in this way, then it means that many qualities one normally associates with cats are yours as well.
The cut on your leg can take on just as many different meanings. Blood being a life fluid, you are obviously either losing vitality from this effort, or you are putting a great deal of vitality into it - perhaps even both. Blood can refer to menstrual blood as well, but I don't get the impression that this is that kind of dream - I just throw it out because I'm not too certain of what it does mean.
The running itself is a compulsion, and at the same time a joy - as if you simultaneously feel that you must continue, but at the same time you want to. I see this as very positive, because there are not many times in anyone's life when what we must do coincides so well with what we want to do.
The best way that I can tie all this together is still a guess, so take it however you will. But when I look at all this, what comes to mind is a creative writing assignment from school. But even if this detail is wrong, there's still some kind of assigned project - you are not quite sure where you're headed with it, but you seem to be having fun.