Well... without going into allot of detail, depression is basically caused by imbalances in the brain... you know, serotonin, norepinephrine... that stuff (I'm sure you've heard this many times.) Yes, sometimes situations can lead to depression, particularly in persons who have these imbalances to begin with. But, my understanding at least, is that you don't have to be in a bad situation to develop depression.

So don't beat yourself up because you are depressed despite not having something happening in your life that you perceive to be a trigger. This is simply a chemical imbalance in your brain that is negatively affecting your mood.

You write that you thought you had beaten your depression. Is there something you were doing then that you stopped doing... or something that you had stopped doing that you've begun again? Perhaps something has changed that has created the conditions that are allowing depression to creep back into your life.

Are you on psych med's? Sometimes these run their course & need to be changed. Do you see a therapist? If not, maybe this would help. Feeling discouraged & defeated, as you describe, are parts of the depressive experience. The main thing here, from my perspective, is not to allow yourself to sink any further into these feelings than you already have. This is not your fault. It's not a character flaw. It's a physiological condition that needs to be addressed in one way or another, either on your own if you can manage it, or with professional help if you cannot.