In OTB chess, it is important to keep a poker face. Stay calm and do not show your opponent that you blundered. I remember a game in which I had a beautiful combination with two sacrifices. I should have won except that I had to play a quiet move in the middle of the sacs. I missed it. A few moves into the attack I realized that there was a defense that I had overlooked, about 3 or 4 moves further on. I kept my poker face and . . . . my opponent resigned!
I remember another game in which, just after making the first time control, I blundered an exchange. I nearly resigned on the spot. But I had a cup of coffee, took my time, looked for the best way to keep any chances, and found a way to double my rooks on the 7th rank after a further sacrifice. My opponent, a future GM, underestimated my counterplay. And he ultimately blundered a queen to avoid mate.
The moral is don’t give up. Don't stop fighting. Don’t let the opponent think you have given up.
@mikewier To stay calm after blundering, you go outsie to play... Or just play Hollow Knight Silksong.

In OTB chess, it is important to keep a poker face. Stay calm and do not show your opponent that you blundered. I remember a game in which I had a beautiful combination with two sacrifices. I should have won except that I had to play a quiet move in the middle of the sacs. I missed it. A few moves into the attack I realized that there was a defense that I had overlooked, about 3 or 4 moves further on. I kept my poker face and . . . . my opponent resigned!
I remember another game in which, just after making the first time control, I blundered an exchange. I nearly resigned on the spot. But I had a cup of coffee, took my time, looked for the best way to keep any chances, and found a way to double my rooks on the 7th rank after a further sacrifice. My opponent, a future GM, underestimated my counterplay. And he ultimately blundered a queen to avoid mate.
The moral is don’t give up. Don't stop fighting. Don’t let the opponent think you have given up.
truth thanks for ur idea