When people do chores or jobs or everyday activities, it might be common to ask yourself: what are other people thinking of me right now? In reality, you shouldn't care. Caring and changing yourself for others is something I deal with, and it something I am trying to stop. Caring leads you to change who you are into someone you're not. Sometimes, people might lose themselves and it can take years for them to find who they truly are.
The first step is to realizing when you are caring. Once you know you are changing yourself to seem better in the eyes of others, that is when you need to stop. Even if you continue to care, knowing when you care is a big first step to stopping.
After all, who cares? People always have things occupying their mind and making fun of you for blowing your nose in class probably is not something of importance to them. The real reason to not care, is because it honestly does not matter.
So be yourself, becasue when you do, you attract the right people who will love you for who you are.