What's wrong with me?

People look at me and they have high expectations because they assume that I am an A-B student, which I was back in the day... But I disappoint. In the past 4 years, I have been slacking. I am not as responsible as I use to be, and that causes me to look inconsistent, and incapable of completing tasks. I had two emotional breakdown. One in mid-June 2015 and the other in late December 2015 (due to a prolonged depressed feeling). What may I do to conquer this?
What's wrong with me?
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