You've got to say no to the things that don't honour you. No to the things that don't bring you joy. And you don't have to explain your no.
How often do you say YES to things that you really do not want to do? Things that you feel you HAVE to do, that you think are your responsibility or maybe you think it's just the right thing to do.
Someone asks you to do something and you feel a 'that feeling' in the pit of your stomach....you don't want to do it. BUT how do you say no? After some deliberation, you decide it wouldn't hurt you to do this one thing for this person.
The fact is, it would hurt you, because it's a lie. It's a lie because you don't want to do it.
How can you do someone a favour, when you don't want to do what they asked? That is not an act of charity, charity comes from the heart. This is an obligation and being obliged often leads to resentment. If you don't don't feel comfortable about it, it just doesn't feel right, if you have too much on your plate, or this person has overstepped, then don't do it.
You don't have to justify yourself to anyone, if you don't want to, you don't want to; and NO means NO. Just say NO, without explanation, just NO.