Empathy: Gift or Curse

To sense a stranger's pain enough to make me stop and grasp again.
Like an unexpected storm the tears stream down my face for one who could meet my gaze and never feel the battle I fight is for him.
For a moment I feel it weaken and then without warning, my heart is heavy again.
Why am I allowed to sense the anguish of one who refuses to face what is his?
Is life a trade?
One soul for another?
Would I go as far as offering my happiness so that he may maintain ignorance of his pain?
Is this a choice? 
Who am I?