Rule No. 13: No Woulda, Shoulda, Couldas

Editor's note: Jim Cramer's new book, Real Money: Sane Investing in an Insane World, is available in selected bookstores now. As a special bonus to RealMoney readers, we will be running Cramer's "Twenty-Five Rules of Investing." For more about the new book and to order it, click here. Today, we present Cramer's thirteenth rule of investing. Read more about his rules:

1. Pigs Get Slaughtered
2. It's OK to Pay the Taxes
3. Don't Buy All at Once
4. Buy Damaged Stocks
5. Diversify to Control Risk
6. Do Your Homework
7. Don't Panic
8. Buy Best-of-Breed
9. Defend Some Stocks
10. Don't Bet on Bad Stocks
11. Don't Own Too Many Names
12. Cash Is for Winners

---

Your head matters in this game. You need to have it on right every day if you are going to see opportunities and act on them. Yet so many of us have heads clouded with thoughts that genuinely throw us off target and make us do the wrong thing. ...