It's about figuring out what you really want and getting it. If you are at a game, and it's really boring, should you walk out and waste what you paid for the tickets? If you apply for a position and don't get it, does it help to decide that you didn't really want it, anyway? If you are looking to buy a new car, what information should you take seriously? There are many pitfalls on the road to making a good decision; rationality is a systematic study of the ways to make better choices in life. Including figuring out what "better" really means for you.

Makes it sound great, but what are the real world benefits? I've been rational for years and it hasn't done anything for me.