I want to hurt my cat when I'm mad

So I know it's not normal, and I think it may be a problem. It's actually not my cat, I have a cat and I never want to or try to hurt her in any way,I love her so much. It's my sisters cat, she lives downstairs and we try to block it off to where her cat can't come up but she always does. She uses my cats litter box which makes me mad, and eats all of my cats food which makes me even more mad. Now every time I catch her up here I pick her up by her throat because I'm so mad and pretty much scream at her... It makes me feel.. Great though.. And I have a problem that it makes me feel like that. I'm scared of why I feel this way and I have no idea what is wrong with me. I won't tell anyone about this because they'll think I'm absolutely bonkers. I know I have anger problems.. But I should never want to actually kill something.. I know I couldn't kill anything I just need to know how to get these feelings to stop, Please help..