You can opt out of being a hero for a couple of minutes, or hours or even for an entire day. And from time to time, you definitely should.
It is very important to be able to say “no” when it’s necessary. You most definitely do not have to carry the entire weight of the world on your shoulders.
It’s your life and you should have the total control of your time. One of the ways you can do this would be to stop pleasing everyone all the time. You should let go of that “If I don’t do this for her, she will think such and such about me.”
It’s a virtue to help others, but sometimes you need to put yourself first. If you need further guidance on this topic, just observe a few cats. You will be surprised to see how cats are amazingly efficient at not giving a damn about the world when they do not want to.