I can relate to your question because at one point in my life I had depression, anxiety, agoraphobia, Irritable bowel syndrome all at the same time. I was a mess. Needless to say, it was a very dark time in my life, I was having a lot of difficulty just functioning.
I know about the downward spiral, some days it seems like you will never get yourself out.
Here is what I learned from going through this in my life.... if it wasn't for God, I wouldn't be here right now, and I also learned a thing or two about my anxiety and depression. I learned that I was more sensitive to things around me compared to other people and I wasn't crazy afterall.
My anxiety was triggered by a difficult event in my life compounded by many more smaller difficulties that piled on. Panic attacks and anxiety was my body's response to this because it was emotionally overwhelming. What finally stopped my downward spiral was the realization that I didn't want to just survive life, I wanted to live it again.
I stopped beating myself up for every little thing I felt was a failure and I started giving myself credit for even the smallest accomplishments like walking to the grocery store and back (when you suffer from agaoraphobia, that's a big accomplishment). I also got mad at my anxiety because it took away so much from my life those couple of years that I suffered. I became determined not to let it win.
During my process of recovery I realized that it was one step forward two steps back. I'd have a great day and almost feel normal, then I would have 2 days after that had me back in my anxious, depressed state. Once I realized that it took me time to get out of the terrible place I was, it was going to take time to get back to my old self, maybe longer and that made me feel better. Eventually I had more good days then bad.
To finally answer your question, I don't think there is one solution to managing your life or overcoming. You have to find what works for you, what inspires you, what gets you through. There are so many great books out there, programs, you name it. For me, my help for managing was God.
I wish you all the best and I hope that others on here can give you great suggestions.