Have you ever lost?

Yes

I think it happened once. It was a two day 5 game tournament, and for one I screwed up a two pawn up endgame, losing (yeah, I was really bad back then, and my opponent was only like a 1400), in a two hour game too, and I was very disgusted that I could play so bad. I get absolutely destroyed by a king's gambit from the black side, and the third was close but ultimately lost (there too, I think I was at some point in good shape: up a pawn or something). I just couldn't stand to play on day 2, so I should have got 0, but for some reason the TD was nice and gave me two half point byes.

And ever since this bad tournament I really strived to improve. And improve I did. The next year of that tournament I won my section undefeated, 5/5, getting a rating jump of over 100 points.