Do periods of misery go away?

I have been in a depressive slump for about 5 years. It seems that whatever I try to hope in, whatever advancement I try to make, to make my life better, it eventually fails and I am back to where I started. I have read such books as "20 minutes in hell" and the author sees people in their own personal "pit" - they are trying to climb out, and some just about make it, but suddenly, a demon claws them back in - this happens over and over and over. My question is, has anyone been here? Has anyone experienced a sustained period in life where things just seemed to be dark - and stay dark? What I am looking for is hope. The bible says that hope disappointed makes a heart sick. My heart has grown pretty sick. One thing I can think of is that I am stuck at this point because there is something I'm not "getting" to move forward - ie: life is a learning experience and I will repeat the same thing over and over again until I get the "lesson". I have an addiction and I keep returning to it - I've lost hope trying to beat it - maybe my God has given up hope on me and I am condemned to my pit with my demons that will not allow me to leave. Is there hope? Will I be able to escape and move on, move forward with my life? I certainly hope so. God, I need to be released from this bondage and learn this lesson and move on with my life. Forgive me, everyone I've hurt or wronged (including myself)! I am truly sorry and I hope that you will forgive me and pray for me, that I may find my freedom. IJN.