NEW YORK (MONEY Magazine) - The oldest adage in investing is "Buy low, sell high." When's the last time you pulled that off? Exactly.

No need to beat yourself up. Selling high, after all, requires you to pull money out of investments that are doing spectacularly well - a move that's both counterintuitive and emotionally painful.

Take real estate funds. As a group, they've delivered stellar returns each year for the past six years. If you own one, it has likely performed better than anything else in your portfolio. And you'd hate to sell a chunk of it now.

But you should.

Now for the even harder part: adding to investments that are doing poorly.

Since the tech bubble imploded in 2000, funds that invest in fast-growing blue-chip stocks like General Electric or Dell have returned, on average, about zip (0.2 percent a year, to be exact). Time to start pouring money in.

By not shifting money, you're increasing risk. No one knows just when real estate will falter or blue chips will recover. But let's face it: The housing boom has waned, and the dividend yield on real estate investment trusts (REITs) has fallen sharply with share prices so high.

"There are very few buying opportunities in the U.S.," says Michael Winer, manager of Third Avenue Real Estate Value, which closed to new investors last year.

By contrast, large growth stocks are trading at valuations that are half of what they were six years ago, and they continue to turn in solid earnings gains. That doesn't mean you should dump all your real estate and bet the farm on large-cap growth funds.

But if you've got more than 5 to 10 percent of your money in the former and, scarred by the memories of 2000, you've been avoiding the latter, it's time to sell high, buy low.

On the buy side, consider the following funds. Three are on the MONEY 65, our list of recommended funds, chosen for their low fees, consistent investing style and solid long-term performance. The fourth is an index fund.

"Profits are improving, and cash on corporate balance sheets is at a multi-decade high," says manager Larry Puglia. "But there's a disconnect between the underlying value of many growth companies and the value the market is giving them."

Puglia sticks with household names such as GE (Research), Microsoft (Research) and UnitedHealth Group (Research). With an annualized return of 2.5 percent over five years, Blue Chip Growth (Research) beats 77 percent of its peers.

This team-managed portfolio is big, with $24 billion in assets, and like the T. Rowe Price fund, it sticks to blue chips.

But thanks to American Funds' strong research group, Amcap (Research) has posted a five-year annualized return of 4.6 percent, placing it in the top 9 percent of its category. Recently the fund's larger stakes included Lowe's (Research), Target (Research) and Wellpoint (Research). The fund is sold through brokers and may carry a sales load.

This fund holds a mere 25 stocks, compared with 100 or more in the typical big-growth fund. Investing in Jensen requires patience. Performance can run hot and cold because the fortunes of a few stocks can swing returns.

In each of the past three years, Jensen (Research) ranked in the bottom third of its category, but over five years it ranks near the top, with an annualized gain of 3.8 percent.

"It's been frustrating lately," admits co-manager Bob Zagunis. "But we're sticking with our buy-and-hold discipline."

The managers look for cheap stocks with a history of high return on equity - a measure of how profitably a company deploys shareholders' money. Among recent picks: McGraw-Hill (Research), Emerson Electric (Research) and Procter & Gamble (Research).

This fund mirrors a benchmark of the largest, fastest-growing U.S. stocks. Growth Index's (Research) low 0.22 percent expense ratio will let you keep most of the big gains that may - or may not - be just around the corner.