How do you let things roll off your shoulders?

Here’s the deal. I am one of those people who likes to please everyone. When I can’t, and someone is upset with me, it literally hurts my health. I can’t eat, sleep, etc..if someone doesn’t like what I am doing. How do you develop thicker skin? How do you stop caring what other people think and take care of yourself? It sounds dumb, but I honestly am wondering how I become someone who not only stands up for themself, but doesn’t let things get to me. Any thoughts?