Why can't I keep my emotions under control?

One day I'm sad and depressed next day I feel good then the next I feel like shit I used to cry every day for so many years but now I'm trying to stop today I just feel depression over me it's just a feeling I can't shake no matter how many times I try to feel better I just go back down how do I get a hold of myself

Why can't I keep my emotions under control?
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