For a number of years I had difficulty saying no. It was a struggle because I didn’t want to disappoint anyone. I wound up doing a lot of things I didn’t want to do. I did a lot of things that others should have done.
Here’s the thing. People don’t always accept no graciously. Sometimes they get angry. Sometimes they act hurt. That’s their issue, not yours.
Sometimes they want an explanation. That’s a slippery slope. If you offer an explanation they are likely to counter it with a solution of their own. No really is a complete sentence.
Saying no gets easier with practice. It’s also easier when you remember that you aren’t helping anyone when you spread yourself too thin.