Think of qualities that you really like about yourself, and things that you don’t like about yourself. I wish I had more willpower, I’m glad that I’m so sensitive, etc. it could be anything that you like or don’t like – the things you pride yourself on and the things you’re ashamed of.
Now, create a character who had those same qualities, but switched. Instead of liking their sense of humor, they hate it. Instead of feeling like they haven’t been doing anything with their life, they look back on all of their accomplishments with pride.
Write a scene about this character, this shadow you. This is a great way to give a character some depth, as well as write about qualities that you’re already very familiar with, in a very different way.