Wearing your heart on your sleeve means you have a hard time concealing your love for someone, or your feelings in general. I once read that wearing your heart on your sleeve comes from a time when people would wear something shaped like a heart (a Valentine heart and not a realistic one, likely) on their sleeve to show that they were in love. I guess it was something like a mourning band, but a little nicer.
But when I hear about someone wanting to give you their heart, I go, "Eww, you're going to give me a slimy, pulsating internal organ? And besides, won't you die without it?" I know they don't mean it literally , I'm just trying to be funny.
That also reminds me of a time I gave my parents a thank-you card that said "Thank you from the bottom of my butt." and inside the cad said "It's a lot bigger than my heart."
True enough. The gluteus maximus muscles are not only much bigger than your heart, they're really the biggest muscles in your whole body.
(I'm not feeling very mature today).