The difference between jiu jitsu and

One of my jiu jitsu instructors had a good description between the difference between jiu jitsu and most other martial arts:

In most martial arts they start you off doing a bunch of punching pads and similar things intended to build confidence. These exercises give you the idea that you are big and tough and could take on anyone.

In jiu jitsu the opposite happens. You spend several years getting pounded on. Instead of walking around with the confidence, you spend a few years walking around worried about everyone because that little 130lb high school student the other day just stomped on you and you just don't know who does and does not have that sort of training.

This is probably a sign of how effective and large a martial art it is. At least for the first five years someone who has been practicing it for two or three more years than you will almost always dominate the fight even if they are comparatively small and weak.