What motivates me are these online calculators that tell you the results of paying off your mortgage early or earning compound interest on savings. It helps me see that over time (sometimes a very long time) these little sacrifices I'm making will really start to add up. Here's an example:
Let's say I want to upgrade my cable package to include more than PBS and Univision. This upgrade will cost $20 and I figure there is $20 worth of wiggle room in my budget, so why not? Well, if I hop on to Dave Ramsey's Investing Calculator and see what $20 a month invested for 40 years would give me at a modest average annual rate of return of 5%, I'll realize that a lifetime of cable TV will cost me $30,647.87 in potential investment. Is it worth that much money to get the Discovery Channel in HD? Maybe I'll just stick to my Seinfeld DVDs.
In all reality there is a good chance I'll upgrade my cable before retirement, but the point is that there will be hundreds, if not thousands, of $20 decisions I'll be making throughout my life and I should consider the long term consequences of each one.
Another Example: If you're a pack a day smoker and quit for the next 40 years you'll save $250,000 by investing that money instead. Plus you're more likely to have fewer health care costs and a better quality of life.
Here are my two favorite calculators to use:
Dave Ramsey's Investing Calculator
Mortgage Amortization Calculator
Comic from www.xkcd.com