Q: At 48 I adopted my son, who is my only child. He just started college, and I'm paying tuition from my Social Security. I'm 67 and plan to work another four years full time, until the mortgage is paid and my son is out of college, and then another six years part time. At the end of 2014, I will have about $167,000 to invest, and will save $18,000 more each year. I need help evaluating how to allocate my funds. Jeanette

The embrace of working longer is increasingly common and it has many implications. Delaying retirement is an incredibly effective retirement planning strategy. For one thing, working longer allows for waiting to file for Social Security benefits. Working longer allows savings to compound longer and, in your case, you can add to retirement savings. Late retirees have to live off their accumulated savings for a shorter period of time once they finally wave goodbye to the workplace.

Still, how to invest your portfolio? I don't have enough information to make specific investment recommendations. Instead, I want to put forward an approach that may help you evaluate the portfolio advice.

For a moment, step back and forget about stocks, bonds, portfolios and investing. Instead, think through what it is you would like to be doing, say, after your son graduates from college? Travel? Volunteer? Work part-time past your current 6-year time horizon? A mix of work, goofing off and volunteer activities? Move to another part of the country? Leave an inheritance to your son, or not? I could go on.

The answer to questions like these will get at the "why" of your life, a perspective that will largely dictate how you manage your money, the "how."

"Your goals and your biography are not simply the stepping-off point for your plan. They are both driver and destination," write Zvi Bodie and Rachelle Taqqu in "Risk Less and Prosper: Your Guide to Safer Investing." "They dictate how high or low you can fly, how black-and-white your plan should be, and how much color and wiggle room you can add."

Bodie and Taqqu counsel matching your income and savings with the timing and costs of your goals. You can set aside money in safe savings to cover your minimum goal-oriented needs. Riskier investments, like high-quality stocks, can be tied to your more "aspirational" wants.

Among the more thoughtful experts on retirement planning and retirement finances is Wade Pfau, CFA professor of retirement income at the American College in Bryn Mawr, Pa. I wrote to ask his opinion on portfolio construction for anyone delaying their retirement. "If plans for part-time work are especially vulnerable to involuntary job loss or poor health preventing the work, then the income cannot be relied on and risk capacity will be less," he responded. "But if one can be reasonably confident that they can do the work they are planning, then they have greater risk capacity and more of their household balance sheet assets are in the form of this stable income source, and so this could justify being a bit more aggressive with the financial portfolio."

Your particular mix of safe and risky investments should largely be dictated by what you want to do with the money and when. With your finances — Social Security, savings, mortgage paid off, part-time income — you have a great deal of freedom to tailor your finances to your dreams.

Chris Farrell is economics editor for "Marketplace Money." His e-mail is cfarrell@mpr.org.