The root cause for the pain in our lives is a dissonance between the is and should concepts. Reality vs. what we feel we should be doing, how and where we should be living. When you feel that something is wrong, when something doesn't seem right, well, there is a high chance that it indeed isn’t.
Sometimes we don't even know what is wrong, we can’t grasp it, it's just there, and unless we change something, it is there to stay for the long run.

Life, most of the time is unfair, we are not born equal, because we are not born in similar material circumstances, so, as a result of that social structures are similarly unfair, and we are presenting widely different outcomes. And we hate it. However, living like a victim is the most disempowering thing one could do. It can lead you astray; you will get further and further from your inner human. Concentrating on what you don’t like is not all the time senseless. Everybody claims that you should focus on what you want and go for it. Never look back! Don’t waste time pondering on your wrong moves, on hopelessness, what you don’t know or, what you can’t do. We hear that so often that sometimes this is a triggering factor for our discomfort because we see ourselves incapable of becoming a jolly good fellow as we should, our optimism is not blooming, and regrets overwhelm us. It is normal. There is nothing we can do about that. Sometimes everybody gets overwhelmed, sometimes everybody cries, sometimes we all wish we wouldn’t wake up in the morning because life seems too unbearable.
You are not alone. Acknowledge it, feel it and slowly get over it.
The hardest thing is getting over it.

Starting everything all over when it seems that everything is lost calls for tremendous willpower. When everything is running smoothly, it goes from inertion, there is no problem, it runs well, but when your wheels get stuck in the mud, the effort required to get everything moving again is more massive. 
It is like modifying a finished garment or trying to repair an old house, where every grind and pipe is rotten. You would have more success building something brand-new, from scratch, than struggling to adjust or improve something already broken. 
Nobody can avoid sinking. Sometimes we all sink, deeper than the Titanic, and with more velocity than a Russian submarine. 

These are facts, fighting back, peeing against the wind, trying to change human nature, our nature is energy wasted. We must remain somewhat skeptical in life. Whenever we are flying high, one must know that there is a deep below. There are no straight lines in nature. Nobody's life is a straight ascending line. There is no need to get freaked out by it. Acknowledging existence as it is, does not mean negativity. It means that you understand how the world works. Have you seen a mountain that goes only up and never comes down? Where there is a peak, it will be a valley somewhere. Peaks are high but usually bear and dry. The view might be nice for a while, but there is no fertility, no flowers, streams, crops. And you are usually alone. As a consequence, you can not stay there forever, so you will stroll down the hill at a certain point. 
We take this as something natural; we don't get depressed by it. 
Why do we assume then that if our life, career, love life is at stake, it will be different than a mountain? It is born from nature, so, it will follow nature's rules. Embrace the valley as much as you embrace the peak.