Wear your heart on your sleeve
If a person reveals their emotions easily and doesn’t try to hide them, we say that they wear their heart on their sleeve.
It is thought that the expression possibly originated from the middle ages, when knights would tie a ribbon or cloth around their arm during a jousting match to represent their lady. The first record of the expression, however, is from Shakespeare’s Othello in 1604.
Fall head over heels in love (with someone)
This expression can be used when someone falls deeply in love with someone, especially if it happens quickly.
“The moment we met we fell head over heels in love (with each other). We got married the following week!”