You start by taking stock of what you still actually do have.
The ego is a great exaggerator, as well as a pathological liar.
Despair tends to communicate with tons of emotion, but with few facts and little accuracy.
Everything, nothing, always, never -- these words are hysterically overused and rarely appropriate. When you hear them being whispered within you, alarms should go off -- you are not listening to your spirit guides, your better angels, or your higher self.
These are angry, wounded words. Remove them from your vocabulary.
Here's Where You Start:
Gratitude journaling. (Oprah) Morning pages. (The Artist's Way)
Sounds awfully simple - real cures usually are.
I have a personalized version you could check out called The Book of Faded Green.
List what you love. What do you see in this moment that is good, no matter how small or how seemingly insignificant. What doesn't suck?
Write 3 pages every morning. It can be in a list form. You can do it in your head while driving or riding the train. The format doesn't matter -- but the thinking works miracles.
A little bit at a time -- one word, one image, one right after the other, every day.
Repeat. Repeat. Repeat.
Leave yourself a trail of breadcrumbs, lead your spirit back out of the darkness, Lantern Bearer. Weave a rope, build a ladder. Rescue yourself with simple observations of gratitude.
Do this until you feel differently. You will. I can't promise you an exact time frame. But I can promise you will.