A cycle of depression

Every once in a while, I feel extremely down on the slumps. Usually a feeling of unfathomable emptiness drags me and I question the mere purpose of my existence. Is this existensial crisis? If so, why do I get it everytime? Sometimes I wonder if people also brush upon the same feelings. Have I dismissed a lot of people to an emotional minisculity that I have to wonder if they also get the same feeling of purposelessness? What really pains me is that my direction in life is a mere pencil sketch that gets to be changed every so often by present influences. I think I have been so frustrated with a lot of unsuccessful endeavors that it created a vacuum of unexplainable angst and feelings of futility.

Yesterday, All my troubles seemed so far away,

Now it looks as though
they're here to stay,

Oh, I believe in yesterday.