I learned to accept the parts of me that no one gets to see. You're not the same person, not 100% at least, when you're surrounded by people. Being by yourself gives you the opportunity to fully acknowledge the sides of you that are buried beneath the person that the outside world sees.
It's cathartic to allow that side of you to come out and take a fresh breath of air, soak in the sun, and bask in the little details that are so easily overlooked because your attention is focused on another person.
Laugh at your own jokes and the little quirks you have, discover that you actually like something you otherwise thought you disliked. Feel at ease when you sit yourself at a restaurant and order for one. Don't be ashamed of not being in the company of at least one more person. Parade yourself around town. Walk like you own the place, but more importantly, walk in full confidence that you're in tune with you.
It's these moments that you realize that some of your insecurities and doubts are so irrelevant, and you start to see how unwarranted it is for you to be so hard on yourself.