I Am Dissappointed I Am Not Where I Want to Be In Life

I had to step down from my role as a team leader due to I could not cope with handling 66 people. I let my myself down, and eventually let my boss down too who say that I could not improve any further by being the team leader. I feel so disappointed in myself and currently suffering from depression. I do not know what do with my life anymore. I have been given the option to go back to my previous role as a LEAD CSR in order to improve on my weaknesses however I have to spend all my energy and drive just to become a team leader again which I feel it won't be worth it. I am not sure what to do any more, and cannot seem to feel better about myself. I feel like a failure.