I learned a very important lesson; it is about tests, success, failure, & especially intelligence. The lesson is:

Failing a test doesn’t always mean that you’re stupid.

Even the smartest people make mistakes sometimes. (Albert Einstein got a few F’s, too!) In fact, you can learn even more from failure than from success. Although I didn’t do so well in my GE101 tests, I still learned some things from the class, like this lesson.
Difficulty keeps you on your toes, but even too much of that is NOT good for you. Take as much as you can handle. When you can do something the easy way, do it the easy way; make the situation less difficult for you and you will solve more of your problems. Think hard until you figure out a solution. It pays to have a backup plan indeed, and if things don’t work out right away, just keep thinking & trying.
As the proverb goes: “At first you don’t succeed, try, try again.”