Failing a CLEP exam obviously isn’t what you want, but it happens and that’s okay. You are able to retake CLEP exams, which means you can always take the three month waiting period in between test tries and study hard, so that you can come back and hopefully do better. The one thing you should be aware of is if your school has a limit of how many scores they’ll accept. If you did not do well, it’s advisable to not send a bad score and wait until you retake the test to send them a  better score.