For me, this typically involves a lot of analysis as to what the obstacles are. There are typically multiple things conspiring to turn me into a slacker and it doesn't generally work to just knuckle down and do it. Figuring out the underlying causes and addressing those is what works for me.

So, you might try spending some time asking yourself 'Why?' x, y or z is failing to get done. Be really honest with yourself. Don't tell yourself anything PC. Then, if you still want to get it done, solve those issues first.