It would be nice if there were a formula for knowing exactly how to arrange your credit. Plug in some known variables and find out if you should have three cards, 10 cards, or stick with debit. It's still more of an art than a science, but we do have a little of the next best thing.
CNBC's Yoni Blumberg recently took a look at how many credit cards people with excellent credit (scores above about 800) have. You actually can play the math a little, because it's not so much how much credit you have, but how you manage it. For example, creditors care a lot about whether you use 80 percent of a low-limit line of credit versus 20 percent of your total available credit, even if those come to the same amount borrowed. (The latter may get you a better FICO score.) If you consistently utilize 30 percent or less of your total credit but you're inconsistent in paying it off, that can affect your credit score too.
Opting out of credit altogether may seem tempting, but it won't pay off ultimately, even if you're really good at using debit instead. And yes, credit cards can create stress, but you'll reap big dividends if you get good at using them well. This includes paying attention to rewards programs and being thoughtful about closing down accounts. There's more to building credit than usage alone. Read Blumberg's suggestions and make it a financial resolution to experiment with strategy and credit. When it's time to check in on your score again, be smart about that too.