Don’t suppress it — feel the hate of losing fully. Watch it — notice how your mind starts attacking you or others. Name it — “This is my ego flaring up. It wants to be the best.” Let it go — don’t follow the thought spiral. Come back to the next move.
Arpad Elo once said something to the effect that players who cannot stand losing are better off giving up chess. They will never play enough to learn to be a good player.