wear your heart on your sleeve

Reveal your emotions so that they are subject to the comments of others. A young man who has a crush on a young lady may tell everyone that he can't live without her, even though his words may be met by his friends' sneers and jeers. If so, he's wearing his heart on his sleeve, which is to say exposing it in a vulnerable place. The phrase comes from Othello, where devious Iago says, For when my outward action doth demonstrate The native act and figure of my heart In compliment extern, 'tis not long after But I will wear my heart upon my sleeve For daws [ravens] to peck at. I am not what I am.