Spend some time thinking about how good you have it. We know this, but we don't often spend time pondering it. Doing so will shape and mold your attitude and develop healthy thought patterns that will make you more thankful all of the time. As the old hymn goes, "Count Your Blessings, Name Them One By One." Take some time and write down every single thing you have in your life to be thankful about. Do this with your children if you have some, and you will all be astounded at all the good things in your life.
Look down the socioeconomic chain instead of up. Focusing our thoughts on the things we don't have, while being a motivator, can also be a source of envy and greed. Focusing, at least on a semi-regular basis, on those who have less than us, causes us to be thankful for what we have.
Go work at a food bank. The more success we achieve, the more apt we are to live our lives around others who are successful while eliminating or drastically reducing our contact with those who are less fortunate than ourselves. Working at a food bank will open your eyes once again to a world you may have forgotten about.
Send a good-sized check on a regular basis. To whatever charity you choose, of course. Richard Foster says in his book Money, Sex, and Power, that money desires to be loved, courted, desired and hoarded. Giving money away breaks the power money can wield over us. Remember, money isn't the root of evil, the love of money is the roots of all kinds of evil. Giving a good chunk away on a regular basis keeps things in perspective.
Simplify. Ralph Waldo Emerson said that the true measure of a man's wealth is in the things he can afford not to buy. When we simplify, we realize how we can make do on so much less. It makes us thankful for all the extra's we have most of the time. Read the classic "Walden." If you really want to get radical, fast for a day or two. You will really be thankful when you get to eat again!
Remember, ultimately what we have has been given to us. Yes, we work hard, but Someone allows us the breath to breathe each moment. Billy Graham was asked what surprised him most about life and he answered "The brevity of it." Life is short. We can't take it for granted. We should remember that life, and success, is a gift. That is something to be thankful for.