Where to start with personal power?
If you feel you gave away your power and want it back, the best is to take small steps. Start claiming back what is obvious. For instance clean your room and personal space and get rid of what you don't want there. No need to be aggressive with that. Remember: you are backed up by a basic natural law.
Gaining back control over your life is a thrilling experience because you start using tools which were always there.
When you do this, you set up new boundaries and simply strengthen your personal foundation. You give power to your base and simply establish a new equilibrium in your life.