Colleagues, leaders, customers, friends, even family are attracted to more positive people. Good vibes and bad vibes are infectious. Stop the bad and spread the good. Pass it on. You're not just helping yourself, but you're also helping others.
Recognition is a great way to keep the positive energy going.
Learning from rejection. Ask the client what you could do differently. Usually how you feel about something in retrospect is your guide on how you'll want it to go next time. You have one life, you must try it all. Everything you do is a learning experience.