I think one of the things I and everyone should keep on learn is decision making.
Decision making is one of the most important things that affect our lives, yet we aren't taught this vital subject in school.
It's quite a fascinating subject, really. A quick search on google websites describes the biases that people are prone to, the psychology of the decision making process, etc.
Our decisions affect our lives and shape our future. Shouldn't we therefore take the the effort to make better decisions?