I have learned from every mistake I have made. Which is to say a lot!
I have learned to design everything in a grow room to be easy to control, clean, repair, and replace.
I have learned not to waste time with weak plants. Clone, Germ and Veg more than I need and flower only the strong girls.
I have learned to name and label every plant and her genetic offspring. Tracking genetics is key to consistent good quality grows.
I have reworked my rooms ventilation twice and hope to have it perfect after the 3rd time.
I have learned after spending a lot of money to try DIY first.
I have learned to clean. Constantly.
I have learned to deal with the occasional appearance of spider mites without panic and stress.
Not bad for a year and a half of growing.
Peace.