Practice random acts of kindness and senseless acts of beauty. One of the best ways to feel good about yourself is to do good things for others. Altruism is a common trait among those with positive self esteem. If you can make someone else feel good it will make you feel good. When I taught middle school I would force my students to be nice to each other.
Some kids only feel good when they are able to put someone else down.
Some never grow out of this. After discussing the importance of self esteem in health. Students would brainstorm ways to feel better about themselves. Eventually, someone would suggest paying compliments to others. So we would practice in class with one person in a the center of circle made by the rest of the students.