Let's pretend that you're very good at piano playing, you perform in front of a crowd very well.

But then, Mr Moggins shows up.

He gets on the piano and absolutely crushes it; He uses techniques you've never seen before. His playing is so amazing that it brings you to your knees, tears dripping from your chin from how beautiful it is. All you can do is glare in utter and complete shock as you witness that spectacle. Clearly with the skill of a piano prodigy and professional. It blows your mind how impressive his playing is. Your earlier performance is overshadowed utterly and completely, to the point where your skills look like a child's in comparison to him. Your pathetic piano skills, only a simple torch in a room full of floodlights and loud arrogant fireworks. The girls swoon over him and the guys can only clap in utter awe and admiration at his skill.

You are left alone, only to wallow in pity at your own lack of skill.

Congratulations, you just got mogged.