Know the other side of the mic. Training to be a controller takes equal parts knowledge, adaptability, confidence, and thick skin. Oh, and did I mention hard work and a thick skin?
Aviation widely relies on the transfer of institutional knowledge. The flight instructor teaching you to fly didnt acquire all his/her skills alone. Someone taught them the basics, who in turn was taught by another individual, and so on. Lessons from past experience (a.k.a. mistakes) enlighten future generations.