A condition where you frequently tap or step on your brakes when you don't need to. Most brake happy people are senior citizens or people that are terrified of or intrigued by everything on the road. Being stuck behind a brake happy person makes you seriously consider driving off of a cliff.
Duder 1: "What the fuck? Why is he braking? There is no one in front of him and this lane doesn't end for another mile."
Duder 2: "It's probably because there's an abandoned tire on the side of the road up there too. He's such a brake happy puss."
Duder 1: "Damn people like this should just ride the bus."