I saw this photo of a billboard in a city several months ago. It says "Yesterday You Said Tomorrow". It has been complete motivation to all those times I've procrastinated or have felt too tired to do something. Each time you say it, you're holding yourself to your own word. I have this photo on my desktop screen and at the refrigerator at home. I believe it would fit as a nice background or lock screen photo on your cell phone as well.
Click the link to see or Google the quote: http://24.media.tumblr.com/t