It's hard to answer in one sentence, because different opponents means different winning tactics. But if I was to summarize it somehow what worked for me, there were always two major advantages that helped me to beat even better players. I was always super fit and I could run the balls for hours and never felt tired. I've done some long distance running in the past even one ultramarathon. It's amazing what fitness does to you. Not only you can run but your eye contact with the ball, anticipation and concentration level improves big time.
The other thing is, I'm a lefty.
I'm a bit older now not as fit as I used to be but I'm doing OK. My game has changed a bit and from a defence to offence player, I became a bit of all rounder trying to shorten points whenever I can.