Don't put all your eggs in one basket.How many times have you heard that expression? A lot more since this whole Enron mess, I bet.It's a good line and a good lesson. Here's why. Good companies can go bad. Bad companies can turn good. The trick to investing isn't necessarily buying low and selling high. It's holding some good names and sticking through the lows and highs. The problem is a lot of pension plans aren't set up that way.Many workers choose to put their entire retirement savings in the stock of the company they work.Many companies choose to compound the problem by matching those contributions in still more of that company stock.That's good when the stock's going up. But, as Enron proved, it's very bad when the stock's going down.Let's face it, when markets turn bad, lots of stocks, good ones included, turn bad too. The same goes for mutual funds. The trick is covering your bases so that when one goes down, something else can, and hopefully will go up.It doesn't always work. But over time, it almost always beats the single-stock strategy.Life lesson: it's not necessarily the hot stock you own today, but the very real money you keep tomorrow.So this isn't about keeping your eggs in a basket, it's about making sure you have a basket to keep them in — period.What do you think? Send your comments to: firstname.lastname@example.orgWatch Neil Cavuto's Common Sense weekdays at 4 p.m. ET on Your World with Neil Cavuto.