What's your biggest investing mistake? In articles listing the steps you must take to be successful in your investing, one that is almost always included is: Avoid making major mistakes. That's why having a specific plan geared to your personality and goals—and staying with it—is so important. It provides the boundaries to protect you from making costly mistakes.

In one form or another, we write about these safeguards all the time here at SMI. We don't always say, "This would be a major mistake. Don't do it." Instead we take the positive approach by telling you steps you should be taking: Follow the Four Levels process for setting priorities. Set your stock/bond allocations according to your risk tolerance and season of life, and rebalance annually to maintain them. Diversify across several asset classes. When following one of our strategies, buy/sell promptly when a change is recommended. And so on.

It occurs to me that it would be very instructive to invite our blog readers to step forward and say to the group: This was my biggest mistake. In looking back over the past 5-10 years, what did you do, or not do, that you now regard as a huge and costly error. I asked this a decade ago, and it would be interesting to see if the top items on the list have changed since last time. Perhaps I'll get enough feedback for another newsletter editorial.

Everyone who shares their biggest mistake in the comments section will be entered in a drawing for a copy of the revised Handbook. And, I'll be happy to inscribe a greeting in it if that is something you would like. So, start sharing! It's been said that "confession is good for the soul but bad for the reputation." But you're among friends...we would never tell.