Mind is the builder...so said seer Edgar Cayce. And it is true. I believe that our mindset has a huge influence on our perception of reality.
That being said, I have used and am currently using an AD...I too have come close to falling off of the cliff. I know my self, I know when I can not do the mind work to climb over the hill of depression, and when that time comes, my doctors/therapist are there to help me and guide me.
I use meditation, prayer, and reading spiritual books/mags to help me keep a positive mindset, with gratitude being upmost in my mind. Yes, even gratitude for the challenges of caring for my elderly in laws, and having MS. Due to these situations, I have had lessons brought to me that have given me great shifts in perspectives, and have also brought wonderful people into my life, including people on this site.
We are dealt a hand in our journey on this planet; it comes down to how we choose to play it. Are we a victim or a victor? We can die doing it either way; it in fact is certain we'll die. Do we want to go with anger and regrets? Or with a sense of a life of wonder and fulfillment?

Not saying it's easy, and you all can point out many posts where I have been in the basement mood wise. But it's possible to live a life of joy and fulfillment, even when ill.

Off the soapbox...great thread, Craig. Blessings to you as you walk your journey...