Shake hands after the loss like you mean it. People remember that longer than the score.

Losing well is rarer than winning well and therefore more memorable. Scores get forgotten within a season, while the way someone handled being beaten stays with everyone who saw it, including the person who beat them. It is also harder, because you have to do it while still feeling the thing.

Decide in advance what you will do in the first minute after a loss, since that minute is when the decision is hardest to make. Find the other person, say the honest sentence, then go be disappointed privately for as long as you need. Both things are allowed.