We learned the hard way about putting our "Easter Eggs" (read: retirement dollars) in one basket. If you're the owner of your own business, don't count on the proceeds from the sale of that business to take care of your retirement.
It's far better to scatter your "eggs" in different places over a period of years. You may lose a few along the way, but you won't lose them all to an unexpected change in your industry that destroys your cash flow, the company's net worth, and your potential retirement nest egg, too.
Be a Fool and diversify. It's never too late.