Place it right after the winning moment in your edit, then follow it with crowd cheering to sell the celebration, and save victory fanfare for the final highlight. If the joke is about losing instead, cut to sad trombone right after the line.
About this sound
This is a short spoken line, about three seconds long, in which a voice admits, 'Sometimes in the life I'm too competitive.' The delivery is self-aware and lightly sheepish, turning a boast about winning into a joke at the speaker's own expense, so it lands as funny and relatable rather than arrogant.