These are perfectly acceptable answers to requests for your time and energy:
No thank you.
Not right now.
Let me think about it.
I don’t have time at the moment.
I’m not the right person to help you with this.
I can’t commit to that.
I won't be able to make it this time.
I'm not comfortable with it.
I'm not interested.
I’m in the middle of something right now.
I’d rather not.
We all have to do things we don't want to do, but most of us do things we don't have to do. I make so many commitments because I feel guilty, I want people to like me, or I want to be important. It's almost never worth it. Insecurity and guilt are terrible motivators. So I'm trying to guard my time a little better. Saying no is hard, but I find it helps to be polite about it, adding a simple thank you or a kind word.
Take care of yourself. Spend your time and energy on things that matter.