Someone wishes you well, Receiver! For life in general, or for those about to embark on some venture, Good luck offers support, encouragement and an appeal to Fortune to look kindly upon their endeavours.
Rooting wholeheartedly for the Bearer, Good luck is a simple gesture of goodwill and care. Responding may be as easy as Thank you or You rock!, but Receivers may also wish to express their feelings about an upcoming event with Fear, Aaaaaaaaaa or Squee, or reinforce their relationship with the Receiver with I love you, I need you, or I miss you. Never again declares the emphatic intent to avoid all related situations in future. Receivers troubled about upcoming possibilities can plead for help with Help! or Make it stop, although whether Bearers will be in any position to assist is somewhat of a moot point.