Wear your heart on your sleeve

Wear your heart on your sleeve - to show your feelings, especially your love for someone.

Example - "Because she wears her heart on her sleeve, it is easy to hurt her feelings"

Image - http://40.media.tumblr.com/7f803f672ba9d4ac2bb108f15e98902a/tumblr_nnvbdzv48I1tib9s5o1_1280.jpg