I've dealt with much of what you've mentioned, however it is unlikely that there is "one thing" that will fix it.
Having one or more good friends that will bust your balls when needed, eating right, keeping a journal of your successes as well as thoughts and failures, and much more besides will be needed.
Having one or more good friends that will bust your balls when needed, eating right, keeping a journal of your successes as well as thoughts and failures, and much more besides will be needed.