Wonderful advice. I have also suffered from depression - thankfully a long time ago. It's simply impossible to "snap out of", as you say - if it was that easy, there would be no such thing as depression, as no one actually wants to feel like that.
I can't even remember how I felt at the time - the only thing I remember was a kind of heaviness that went right to my soul. There were several reasons why I managed to get out of it, but it was a complex procedure. All the things you mention are very helpful.