I think everyone must go through this, at least to some degree. Some are perhpas more fortunate to have a better support system than others. Or, perhaps, have learned better ways to deal with it. There is an excellent Ted Talk by Jane McGonical, about how she struggled with this and found a way to improve her life. Well worth watching. One other trick, is that your mind tends to dwell on things for about 2 minutes. So, if you can divert your thinking to something better for 2 solid minutes, then you might be able to pull yourself out of a down moment. A good way to do this is, to start thinking of something positive, and if the old thoughts creep back in, then gently start over with the 2 minutes. At first it make take 5 or 10 restarts. Then, over time, with more practice it gets easier. My last tip I wanted to share is one I stumbled on purely by chance. I was keeping a journal for some sports I wanted to get better at. I would write down my eating, sleeping, and what exercise I did, for how long, and how intense the training was. After a few months I was reviewing my notes and I happened upon a pattern that related sleep and strong emotions. In this case, 2 weeks after a very short night of sleep, I would have a day that I would describe as heavy, or emotional. Imagine that, 2 weeks after a short night and you have a bad day. So far I have not seen this written or talked about anywhere.

I wish you the best of luck, and just by you asking, it should help to find a way to make this part of your life better.