There are so many factors that can decrease your credit score. One in particular is your credit utilization rate. Your credit card utilization rate is the ratio of your credit card debt to your total credit card limits.
Now, if you decide to close any of your credit cards, it could cause your ratio to increase, and therefore your score to go down. Essentially, when you close a card, you reduce your overall available credit.
You should be in good shape as long as you keep your credit utilization below 30 percent. This will show lenders that you’re using credit, but not dependent on it.