If you wear your heart on your sleeve, it’s/its hard to hide your feelings. Whether you’re happy, angry, or bored—it’s/its obvious to everyone around you.
Where does this phrase come from? It’s/Its origin is likely medieval Europe—specifically, jousting tournaments. In these games, knights on horseback raced toward each other holding long, pointy sticks called lances, trying to knock each other off their horses. (Ah, the good old days.)
If a knight was courting a lady, he would tie her ribbons around his arm as a public declaration of his feelings. He would, in other words, wear his heart on his sleeve.