 Your ability to earn. And you can be flexible with the amount of hours you work. I mean, if you have that ability, that is one of the most powerful pieces of a financial plan. It sure is. In my opinion. All right. The next thing on this list, again, this is the way retirement is changing. People are living longer. Human life expectancy doubled between 1900 and 2000. In fact, up to half of those who are currently five years old are likely to live to the age of 100.