Source : Webster's Revised Unabridged Dictionary (1913)

Heartsick \Heart"sick`\, a. [AS. heorise['o]c.]
   Sick at heart; extremely depressed in spirits; very
   despondent.

Source : WordNet®

heartsick
     adj 1: full of sorrow [syn: {brokenhearted}, {heartbroken}]
     2: without or almost without hope; "despondent about his
        failure"; "too heartsick to fight back" [syn: {despondent}]