With the end of the year nearing, many financial planners will be telling their clients that it is time to "rebalance" a portfolio. Rebalancing means going through your portfolio and making sure the weightings you have for each stock and asset class make sense.

My advice on rebalancing? Don't be so quick to rebalance. Indeed, conventional wisdom is not always right.

My take on rebalancing is a bit different than most in the financial-services industry. Conventional wisdom says things like you shouldn't have more than 10% or 20% of your portfolio in a single stock, that everyone needs bonds, that you need 10 mutual funds and 50 different stocks in order to be properly diversified.

Don't believe conventional wisdom.

The reason I hate to rebalance is that rebalancing means selling your winners. Indeed, if you bought a stock that now represents 30% or 40% of your portfolio, chances are that stock has been a big, big winner for you.

I have a problem with selling your winners - your best stocks - just because they now make up a big portion of a portfolio. True, if you are someone in his or her 60s, you probably need to be careful about having all your eggs in a single basket. But someone in his or her 30s or 40s has the ability to assume a higher level of risk by having a more concentrated portfolio.

Remember - the biggest fortunes in this country were made off the backs of just a few holdings. Don't let simple percentages tell you what stocks to sell. Evaluate the merits of each of your holdings and buy/sell accordingly.