I set my benchmark really low and if I complete it I consider that I've met my expectations. For example for working out I tell myself that I'll only do 5 pull ups and that would be success for me. I always end up doing proper workout once I get started. It can be applied to other things as well.
The way the human body is built we are often distracted by physical needs. For example hunger, thirst, uncomfortable temperatures , aches and pains and not enough sleep. If your having a very difficult time getting motivated are those needs being met? You need to take care of yourself to have your body and brain function efficiently.
Also listening to music, chewing gum, going for a walk, giving yourself a small reward like that helps as well.