My best example is how I became extremely good at Excel. I consider it the best example I have because I used to hate Excel. I used to see it as the annoying part of Microsoft Office. It used to be the software I don't open or care if it exists on my PC. And when I got my business data analysis job role it gave me lots of headaches and I felt like I have gotten a wrong job, a job I was not suited for. But my boss and the clients I was reporting to didn't care what I felt or what I could do; they kept asking for impossible Excel reports and I was forced to learn how to make those impossible reports. After 6 grueling months I became good at Excel. The whole story suddenly changed. I no longer waited for my boss to ask for an impossible report, I went online to freelance sites and attempted the impossible tasks people were asking to be done via Excel. I started using Excel for stuffs I never thought possible or reasonable. And the result: I became extremely good at Excel. All because my boss thought of no limits while asking for reports from me and I attempted all the impossible and unreasonable Excel projects I came across. I destroyed all the boundaries I used to have. I became like the child who was given a hammer and saw every other thing as a nail: I think first in Excel even before thinking in English.
The attitude of attempting all you can, whether feasible or not, is the one guaranteed thing that will turn you into a pro at anything. When you keep stretching yourself and constantly attempting the seemingly impossible and unreasonable you will inevitable become a guru at anything you desire to be a pro at.