Struggling with Depression: Feeling Tired of Life

It's been a long week. I'm upset that I can feel myself slipping into another depressive episode. I'm growing apathetic toward life again, and my schedule is too busy to afford that. And, yet, all I want to do is cancel all plans and sleep. I want to sleep, not due to the exhaustion, but simply in desire for avoidance; it's just easier to be unconscious. I'm tired of life all over again. It's exhausting when life is a never-ending dance of "one step forward, two steps back". I constantly think about the quote, "most people die at twenty-five, but aren't buried until seventy-five". It seems the most apt adage to describe my life. I truly feel like my life ended at age four, all the following years have just been waiting. I'm not actively wanting to die, but I no longer have any drive to want to start living either. How do you choose between life and death when both sound as stale as the other?