The financial decisions we make on a daily basis, even some relatively small ones, can have a huge impact on our future. That's because of the power of compounding. We understand that a relatively small sum saved over time can grow into a very large amount in the future. But we rarely recognize how compounding can work for or against us in our purchasing decisions, which are more frequent and significant than savings decisions. This is an area where the concept of opportunity cost can be especially helpful.

I'll be the first to admit that the idea of "financial planning" can sound about as exciting as an invitation to a friend's daughter's third grade violin concert. Throw in the fact that we are in-the-moment creatures, not naturally focused on the future and we begin to understand why planning is such a challenge for us. We are so busy managing the chaos of our daily lives, we simply can't afford to take the time to consider a future that seems to be coming at us faster than we can adjust.

If you visited the Yahoo Finance web page on Wednesday, you may have seen this headline: "Dow 6,000: Wild prediction or worthwhile caution?" The article behind the headline is about a guy named Harry Dent. Dent has made a number of market predictions over the past few decades--his...