It's getting harder just to feel alive

I wish I had some clue about what is happening to me lately. I feel like I'm slipping back into a black hole. I feel like I'm losing my sanity again. I just don't get it. I had started to come out of my depression. I had started to see the light at the end of the tunnel. Everything looked like it was getting better. Then everything came crashing down suddenly. It was seemingly out of the blue.