I used to be scared of speed bumps...

I used to be scared of speed bumps but I’m slowly getting over them

This joke is a pun - to "get over" something is to accept something that is unpleasant as being inevitable, however if you were to travel over speed bumps in a car, it is considered a good practice to travel slowly as you go over them in order to not damage your car. This pun uses both senses of the phrase.