Disappointment and depression

Sometimes, I just can't help but feel absolutely low. Because for some reason or another, I just didn't do what I wanted to do.
Writing this down does actually make me feel so much better. Because I'm doing something now. But there are times when I don't do anything, and as a result, I feel like I'm an absolute failure. Just know, I stopped working on something because I felt too tired to go on, and I feel like I've let myself down badly. I want to finish it off, but I can't because I'm too tired. I should have done it earlier, I tell myself, I should have been more organised, I should have realised. I won't be able to do it tomorrow, as I'll be tired out due to a physically active day. I won't be able to finish it until the last moment, and then I'll really be tired, after staying up till dawn in order to complete it. Why did I procrastinate, why did I put it off til last, why did I do that when I could have finished this.

But what I try to tell myself is this. That what I do is up to me, not up to my workload. That every thing I do is a conscious choice, rather than an inbuilt mechanism, and that if i want to do something, I can do it. I won't fail. It is possible, and I can do it. And further- to hell with the work, what I do in my time to make my life better is far more important than whatever it is someone tells me to do. And that's the last word.