Boston Celtics rookie wing Jaylen Brown had a tall task in this past season’s Eastern Conference Finals: guard LeBron James. He was nervous. Guard the greatest player of his generation in the playoffs? During his rookie season? If he didn’t somehow mitigate his pre-game anxieties before tip-off, he’d have already lost half the battle. He finally settled on an unorthodox solution — to create a three-minute, 31-second rap song that he rapped, produced and composed himself, one that would boost his self-esteem and get him past the urge to vomit before games in nervousness. Brown listened to the song, entitled Building Blocks, several times before all five games of a playoff series in which he held his own against James defensively.