About the time I reached my late sixties I stopped worrying about what people thought. If they don't like the way I look, act, think, etc - fine. I don't care.
How to not care what people think..? I always feel as if someone is judging me for what I wear, how I act, etc..
What impact does this person have on your life?
If it is a Mentor, or someone you idolize from afar, maybe I can see why you would care. You are just as important as anyone you see around you . . . Make sure to put yourself (psychologically) on equal footing with your peers. Sure they may have a strength you lack, but I bet they have some weakness that are your strengths.
You need to "Love Yourself" . . . Seriously, look in the mirror and say "I LOVE who I am. Sure there are things I want to get better, and that is just a matter of time. Those things I can't change make me unique and not just another drone or lemming in the world!"
Give yourself a hug, and every now and then . . Treat yourself to something special . . Because you deserve it.
It may help to realize that pretty much everyone else is also caught up on how they look and act. Far too much so to really pay you any mind.
You have too put things into prospective. If the person has no impact on your life, honestly why should you care what they think? I only care what my husband and my mother think. After that...I don't care because they are not that important. Now if I worked or had children, I would care what they thought.
How to not care what people think
Search with that phrase and you will get a lot of links with suggestions.
---Peruse at your leisure
You are an unrepeatable experiment.
Some day you'll be as far away from all
of them as the moon. Learn all you can.
Laugh often, and love with all of your heart.
Your gonna be just fine.