What is motivation?

Having been hideously over worked in the last few months, I am wondering what is the definition of motivation. Times have been quite tough of late and it makes one question one's beliefs, fabric and ethics. I strive to do everything with which I am tasked and with which I task myself to the best of my ability, within reason, of course, but am currently questioning why. Why bother pushing myself when there is no reward forthcoming? Why do any more than my hours? There are no long term career prospects in my office. Recent events have clearly illustrated that I'm not secure in my job regardless of how well I perform. There will be no raise this year and only sufficient bonus to purchase a Mars Bar for the outstanding performers. I am far from a socialist but am curious about the benefit of working to rule. It would likely only last a day as it rather contradicts my ethics but maybe I'll try. Once my current project is complete , of course!

At the very least, I need to redress the work-life balance. 14 hour working days are not good for anyone...