up + down = BALANCE
What makes a negative emotion unjustified is that it either outlasts the causitive event and no longer serves a purpose, or it descends upon you without an apparent external triggering event. Only after allowing it guide thought processes does the negative emotion appear justified.
My personal method for coping with negative emotions is to accept them, rather than resist. This may seem counter-intuitive or counter-productive to some but my attitude is that UP can not exist without DOWN.
There are some people, who have been DOWN for so long and so deep, that they do not realize nor remember there is an UP. The opposite is also true. I prefer to be UP and I realize that DOWN is a naturally recurring state provided to impede my urge to fly higher and higher, which can result in mania, the opposite of depression.
Since I prefer to be UP and I can accept DOWN, it is easily inferred that each state is my choice, my option. I BALANCE the two states, in my favor, by applying a time limit to my DOWN s. Knowing the negative effects of the DOWN, I set aside some time to indulge, because I can do little else in that state. I set a time limit, an hour, an afternoon, at most a day, and then get into being DOWN
When DOWN had its alloted time, I thank it for the experience and then choose among several techniques for releasing it. A two or three kilometer run always did tthe trick and now a two or three kilometer walk has the same result. Some people eat chocolate, for the caffeine/sugar boost but I have learned that soybeans are much better for my brain chemistry. Singing works for some; I sometimes chant a mantra, while I walk through the forest.