Too much or too little salt. Salt is one of the most magical ingredient known to mankind. It can make all the ingredients of the dish shine like stars. It can also f@#k up all your hard work by overpowering the other ingredients. Cooking, like every other thing in the world, is about balance. It is the art of balancing flavors that compliment each other
I'm happy you got that passive/aggressive thought off your mind.. Cook on, big fella.
#6 Grocery store chills some vegetables but not others, I do what they do.
#9 Mix sauces similar to mixing paint; alternate top to bottom and outside edge inward.
#12 An accurate meat thermometer is a crucial tool. Learned my lesson after I overcooked a good piece of meat.