With this morning's news about the takeover offer for PetroKazakhstan (NYSE:PKZ), I couldn't help but wonder if my portfolio would be better off if I drove my bike into the river on my way to work one of these days. I'm 99% sure it would be better off without my sell recommendations, anyway.

The Canadian-Kazakh petroleum producer is only my most recent demonstration of how to lose money by selling too soon. Sure, I made a nice, fast, short-term gain on this stock a few months back when I rode it from the $30s to more than $40. Then, I watched with interest as it cratered, down past where I'd bought it, even into the mid $20s. Today, it sits around $54 a share, meaning that my haste cost me another 31%. (If I'd had the guts to buy in the $20s, rather than just indulge my smug satisfaction, I could have gotten a quick double on those shares.)

I've got similar stories with a bunch of other stocks. For instance, I purchased Motley Fool Stock Advisor pick Reebok International (NYSE:RBK) in the high $30s and sold for a small gain after growing weary of waiting for sales to perk up. That's it. That was my entire excuse. Sales were so-so. The business was running just fine. I simply got bored.

The boredom cost me. Earlier this month, the other shoe finally dropped when a takeover bid came from adidas-Salomon, and bang, the shares now trade for $56 each. Another 33% left on the table.

Motley Fool Hidden Gems pick CNS (NASDAQ:CNXS) was another cash flow cow that I owned to my eventual boredom. I sold, again, for a small gain, and since then, the shares have doubled.

As I go back through my list of throwaways, there are only a few I don't regret. One is Buffalo Wild Wings (NASDAQ:BWLD). Another is Harley-Davidson (NYSE:HDI). Though both are up since I sold, meaning my portfolio might be worth more had I held them, I found the risk/reward ratio to be skewed beyond my personal level of tolerance.

About the only stock throwaway I can find that makes my sale look prescient is MIVA, an online advertising outfit that used to be called FindWhat.com. Though this one sailed into the $20s after I made my small gain, it now dwells in the cellar around the $5 mark, a couple bucks below where I took my initial position. In the end, I felt that it didn't have what it took to compete against peers like Google (NASDAQ:GOOG) and Yahoo! (NASDAQ:YHOO), and for the time being, it appears that the Street agrees.

The moral of the story is that getting rid of good companies is a tricky business. That doesn't mean never sell. Just remember that holding good companies is the key. Holding them. You never know when the rewards are going to come, so as long as the business is operating as you expect, let your winners run.

This month's issue of Motley Fool Stock Advisor begins with a discussion about the hazards of selling too soon, from two guys who know the pain: Fool co-founders Tom and David Gardner. A free trial will get you their latest picks, and advice about how long to hold.

For related Foolishness:

Seth Jayson is patenting a duct-tape-based device designed to prevent needless stock sales. At the time of publication, he had no positions in any company mentioned here. View his stock holdings and Fool profile here . Buffalo Wild Wings is a Motley Fool Hidden Gems recommendation. Fool rules are here .