My self-control is so low, I feel like I'm a lost cause and there's no hope

I can spend an entire afternoon playing Plants vs. Zombies, but I just can't get myself to study or work.

I don't want to be this useless person, but I truly can't get myself to take any action at all.

My therapist says it's because I'm depressed that I'm like this, but I think I'm depressed because I watch myself deteriorate and have absolutely no self-control to change it.