Where I'm from we have the phrases "You run your mouth a lot", "Stop running your mouth!" This means that a person talks a lot, but in a sense of trying to get a phsychological advantage over the opponent in a game/contest/competition. The person 'running their mouth' would say stuff like: - I'm going to win easily! - Why do you want to play another match, do you enjoy losing? - Ready to lose? Is there anything similar in Spanish?