1. to make your feelings obvious, to show vulnerability, to reveal opinions
People always know when I'm upset, I wear my heart on my sleeve
When you 'wear your heart on your sleeve' you are being open and vulnerable by being honest about your true feelings or emotions. This phrase was originally associated with romantic feelings but can be used to talk about being honest or frank in any situation. Wearing your heart on your sleeve may mean behaving in such a way so that your feelings are obvious or telling others directly how you feel about something or someone. This is an idiomatic expression used mainly in social contexts though there are many professional applications also.
I know exactly what topic Jenna will choose for her Project, she always wears her heart on her sleeve.