Once, a consultant I had gave me good piece of advice that helped me when I was in deep depression. I'd like to share it here now.
Quite often, in deep depression, nothing seems to work and you feel at the end of your tether. You're maybe unable to 'do things' and depression just holds you down all the time. The following 'tip' may not help when the depression is light or moderate but there's no harm trying it anyway.
In such a situation, you want to get out of it, and something has to change. 'Change' seems like such a big thing that you just don't feel you can do it. So, try it in really small steps. You can easily change the circumstances around you in very very small ways. For example, at the most mundane level, change the way round the loo roll is on the holder. Move some ornaments around. Move some pictures. Change the way you hang up a towel. Clear out a cupboard. Light a candle in the evening. If you have a garden with plant pots, move them around a bit. You choose the 'level' of change that you can handle, and some of them above anybody can do easily and quickly. The result (should be) that you feel a sense of achievement and that change is possible.
Hope it helps you if you need it.