Normal is relative. What's normal to bạn may not be normal to everyone else. People can be sadistic without being sent to an asylum. I have sadistic tendencies but I won't go out and murder a town hoặc anything like that. As far as I am concerned as long as bạn don't try to kill people hoặc mutilate them hoặc anything like that. I think you're fine.
I mean everyone to a degree has the possibility to be sadistic. bạn might need to try and practice empathy towards people thêm often but I don't think you're that bad for being happy when someone cries.
I guess I'd need some thêm details on your mindset, like: are bạn the one making others cry? Is that the only thing that brings bạn a sense of happiness? If so, then you'd probably want to be concerned.
As far as feeling sadistic, I think we all feel a range of emotions. If this is the only way that bạn feel, again, bạn should be a bit concerned.
I entertain dark thoughts as much as the tiếp theo person, I suppose, but they don't occupy my mind constantly. I also laugh at inappropriate things, but I think that's thêm a nervous reaction. Well, that's MY story anyway.