How do I learn to live for myself again?

How do you learn to enjoy your own company and do things for yourself? For three years everything I've done was to show my boyfriend (now ex). I'm talking personal achievements and fun stuff too (drawing/good grades/maintaining my aesthetic/etc). I can't seem to learn how to do that for myself. All I do is rot these days because there's no one to seek validation from. Plus, I'm honestly afraid I won't find anyone after I improve and glow up, so I'm scared of even trying. I'm a very young adult and I feel like I'm wasting my life.