I'm going to say no to my mother
That may be a good thing. What are you going to say no about?
She always wants to know where I'm going and what I'm doing so I'm goign to refuse to tell her.
Wanting to keep your life private from your parents is understandable but they ask those questions because they're worried about your safety. Think about that and try to show more respect because telling them doesn't hurt and you're just being petty by refusing.
I will do what I want because they're old.
I think you should respect them a little more, being old doesn't mean that they can be mistreated. While your privacy still matters, can you try to think like them? They just want the best for you and maybe you can try to show your appreciation to them.