[validate] Random Success Message

[validate] Random Success Message

I am using the jQuery Validate plugin and trying to generate random success messages. Eveything is working with this code. 
  1.  var messages = ["Good!", "Great!", "Awesome!", "Super!", "Nice!"];
    function successMessage() {
    return messages[Math.floor(Math.random() * messages.length)];
    }


and then:
  1.  success: function(label) {
          label.addClass("valid").text(successMessage());
         }

The problem is that the success message is being called on keyup so it is generating a success message with each keypress or when you click onto then off of a field. I tried this but it didn't work
  1.  success: function(label) {
         if(!$(this).hasClass("valid")){
          label.addClass("valid").text(successMessage());
         }


Any help would be great