>why the fuck do I enjoy horrible things but get depressed by cute things?

Because you are Evil!

Just joking ^_^ More seriously, I think there are a few points to be considered: have you become extremely impulsive? If not I think it's ok, but if yes then you should take it more seriously. Also, it's important to consider if your judgment is getting cloudy: if you see an object at a shop, it's ok to desire it, it's not ok to steal it. If you want to hurt kittens, but know that you should not do that, and won't allow yourself to do that, then it's fine.

Why don't you find an escape vent to empty your dark urges? Something like writing horror or gore (why do you think people write that kind of stuff), or read/watch movies/books, or do some sports in which you discharge your rage (a punching bag seems like a good gift for you, at the moment).