In my opinion, low self esteem is rooted in not being able to accept yourself for who you really are. When I'm feeling self conscious or get rejected I often try to think "What would my best friend say about me? Or my husband?" And then I try to use that as a launch pad for why I should love and accept myself. You can start small say "I may not be perfect but I do know I really like _________ about myself" then slowly reaffirm this fact to yourself until you know in your heart it's true. Then find another thing you like or do well and slowly build from there. Believe me I know its hard, it took me six months just to accept the compliment that I have beautiful eyes. People would comment on it from time to time and I always thought they were just being nice. It wasn't until I took the time and did the hard work of starting to love myself that I started to gain confidence. It's baby steps though, but once you start, the momentum will build and before you know it you'll have a whole list of things you like about yourself. Good luck!