King's Indian Defense, Makagonov Variation (or Why Not to Underestimate Your Opponent)
This is a short game I lost with Black. In a King's Indian Defense White played 5.h3 which looked a bit passive (though it is actually fine). That's where I started to look for a way to exploit what I thought was an inaccuracy. But I was looking for something that was not there. As I had wrongly evaluated the position and expected that there be an active line to favor me, I went for a complication in a sharp line that I couldn't calculate to the end. My opponent played correctly and gained an advantage, and then I resigned. I believe I wouldn't have gone into that mistake if I hadn't underestimated White's move.