Would you be able to kill a person?

I'm a very nervous person. That's why I might. Even over something trivial, just because I miscalculated my strength. The first time I hit someone, I cut their eyebrow deeply because I hit them with my head against a table. And all because they popped a balloon behind my back. I had warned them and asked them not to do it. So, I'm just afraid of hitting someone... because I'm afraid that, due to carelessness and nerves, I might accidentally kill them.