Everyone in their own right is a master of something, whether they be specialists at it, something they specialise in or something they are extremely good at say with memory for an example.
It can range from things of both physical and mental forms. Perhaps you are the master of skateboarding, you might be a master gardener, a master driver, a master of your emotions, or a master communicator.
You have developed this praise of title from more than anything your hard work and practice towards the hobby or profession, and it is based on your service and quality of production that will determine if you are a master of something or not.
Using a service such as carpet cleaning for example. If someone takes 3 hours to clean a house, doing a very poor job, and charging extensively, they would not be a master of carpet cleaning. However if you managed to grab a cleaner who did the job twice as good in half the time, for a reasonable price then he would be the master.
So in your life what are you the master of? Or who do you know is the master of something, and what might that be? Mastery can be for good, for bad or for the simple fact of possessing the ability.