I'm going to cheat on a math test
Is there a reason you want to cheat on the test?
I'm too dumb to understand the material.
There is no valid reason to cheat on a test. If you have the urge to cheat on a test you should think about trying to study more in the evening.
WTF I can't help it and it's perfectly fine to do so.
It is not fine. If you don't understand the material, get a tutor and ask your teacher for extra help.