Kenneth Fisher says that if investors really want to help themselves, they should buy stocks — and wait.

“What is the most common investor mistake?” Fisher asks in his latest Forbes column. “Trading — getting in and getting out at all the wrong times, for all the wrong reasons. … Most mutual fund buyers, for example, badly lag the very funds they buy (and sell) because of bad timing.” Over the last two decades, he says, “stupid switching into and out of funds has cost equity fund holders more than four percentage points in annualized returns and bondholders even more — nearly six percentage points.”

Fisher says the average mutual fund holding period for equity or fixed income of about three years is “too short”, as well. “The solution, of course, is to trade less,” he says. “Buy into good, well-researched companies and then wait. Let’s call it a sit-on-your-hands investment strategy.” He offers several picks that he says fit the bill, including Apple.