Do not even try to park on downtown streets in Brussels if you don't like fighting.

Belgian drivers are the rudest drivers in the world. The one time I tried street parking, they would zip in and block the spot when I was trying to back in and parallel park, as but one example. Then they start yelling at you. Apparently, you are supposed to yell back, and maybe get into a fight. If you enjoy that sort of experience, you'll be right at home.

If you don't enjoy doing that, pay the money, but be prepared to fight in the garage as well if spaces are tight.