"Outsmart your brain by knowing when you are wrong":
Humans are incredibly bad at summing up a bunch of small numbers. I had recently read a study that looked into why people are so bad at this task, but the important part was people commonly underestimate the total.
Knowing what you are bad can be incredibly important. Use this trick when estimating the timeline for a lot of small tasks, or figuring out what your monthly expenses are. It always seems shocking your credit card bill is so high when it is a bunch of small purchases. Learn what else your brain cannot perform well and use that to your advantage.