What can I learn/know in 10 minutes about your profession that is useful for the rest of my life?
Do not trust ad-hoc security mechanisms.
People like to think that being able to build a secure system is function of how smart one is, and implicitly assume that they are smart enough. But something secure is a skill that has to be learned. In cryptography - for an overwhelming portion of the cases, it shouldn't take a skilled cryptanalyst more than 30 minutes to break a system that you home-brew by yourself. My limited experience in other fields of information security shows that this is common across the board.
So, the lesson here is that if you need to secure something, consult an expert and don't try to DIY.