What it's like living with clinical depression

As the title would suggest this article is about depression, not how to manage or cope with said disorder, but merely what it is like to suffer from it. Note that it is very difficult to explain depression to someone that isn't suffering from it, hence the mass misunderstanding that depression is just some garden variety sadness that can be fixed magically by talking to a shrink or taking ssri's; but depression isn't that easy to overcome unfortunately, and many suffer their entire lives, never truly defeating this illness. Because of the lack of real understanding from the general public, and the difficulty of trying to explain these feelings to others, many who suffer from depression feel isolated and alone, which only makes the entire situation worse.
When I first told my wife that I was depressed and was thinking about seeking out professional help she was not very understanding of the situation. This wasn't her fault exactly as she believed that depression was a form of sadness somehow influenced by outside circumstances. Even though I tried to explain to her the real root of the problem I could not and she blamed herself, and also me for my suffering. this was one of the worst phases I have ever experienced regarding my depression, as I felt that I truly had nowhere to turn. This put a great deal of strain on our marriage for almost a year before I finally went to a therapist. I honestly don't remember how my first therapy session went, I only remember leaving and feeling more broken than I had ever felt before; it was shortly after this that I began to spiral.
I began trying anything I could to feel some semblance of happiness, drugs, alcohol, everything. This obviously helped nothing and I spiraled even further, this was absolutely my lowest point. Every time I would feel a little happiness, it would be replaced by an huge hole, a void that could not be filled, only briefly fed. It was during this time that I realized I was broken, damaged beyond repair, and thoughts of suicide started creeping in. Luckily for me (even though I could not see it in the midst of my spiral) I had a semi decent support system and was placed into a rehabilitation center to curb my substance abuse and also help with the underlying cause of the abuse.
This was a great time for me, and for the first time in a long time I felt hopeful and even happy. I graduated the program and was released back with my family; I was shocked at the seemingly instant loss of my newfound hope and happiness. I was sure that this had fixed me, that I was no longer broken, and yet I was just as damaged as I had always been. The last twenty years have been a repeat of this same cycle over and over again, thinking I've finally found my happy ending, and then being forced to realize that I was wrong.
Depression is a literal hell that I have lived in for my entire life, and will probably never overcome. I have found ways to cope for the majority of the time, but when I'm alone and idle... that's when it really eats at me. At times it can be crippling, and the worst thing imaginable, but a lot of the time its just a dull, nagging, empty, sensation that's almost impossible to explain. In a way my desire for happiness is the cause of my depression, and I don't know how to fix it.