Holding a stock with major gains is nothing short of being just plain greedy. Investors must take some off the table. And in Cramer's book of rules, greed is bad and discipline is good. Strict discipline leads to the ability to cash out when you're winning.  Of course, Cramer understands wanting to stick with a winner, wanting to let it ride. Nobody likes to forfeit gains, and that's how selling a winner can sometimes feel.  So, the next time you see a stock climbing ever higher, change your mindset to see your stock as getting more and more expensive. Eventually, it will become so expensive that it won't attract new buyers and will start to go back down.  And you want to be out by that point. It's a simple case of buying low and selling high. Kind of.  Yes, it would be ideal to sell at the very moment a stock tops out, but the odds of that happening are very unlikely. But it's all about instincts.  ----------------------------------------------------- Read More from Mad Money with Jim Cramer Cramer Remix: Wanna invest in 2015? You need this Cramer's No. 1 most important lesson in investing Cramer: Buying gold is the way to go -----------------------------------------------------  Therefore, when you have a large gain on a position, find a level where you can feel satisfied with what you have. Then take at least a portion of your bet off the table. Otherwise, you put your gains at risk, and Cramer says that's piggish.  "When things get crazy expensive and I know you have a lot of gains, you will hear me say that you are being a hog, and the bottom line is that I don't want your head to be in this guillotine when the party ends and big wins turn into losses," Cramer added.
If you own stock, there’s nothing better than a big gain. But too many investors put those gains at risk.