Source : WordNet®

cheer up
     v 1: cause (somebody) to feel happier or more cheerful; "She
          tried to cheer up the disappointed child when he failed
          to win the spelling bee" [syn: {cheer}, {jolly along}, {jolly
          up}]
     2: become cheerful [syn: {cheer}, {chirk up}] [ant: {complain}]