[sanityinc]

Most people tend to automatically reflect back at others the emotions projected towards them: someone gets angry at you, and you get angry right back at him. Being able to notice this in the moment and sidestep the reaction is a learned skill.

On the opposite end of the scale, there are "sponges" who receive and absorb others' emotions unconditionally, as you describe. I've known many people like this, and many seem to develop unusual health issues -- but it's equally possible to notice this process in the moment and modulate it.

In both cases, practicing mindfulness meditation is the most direct way to develop the necessary skills.