According to online dictionary ,
Don't worry, be happy !(encouragement)
くよくよするなよ。ほら、明るく明るく!(励まし)
but ... I think ... how to encourage depends on each speaker. so In my opinion, "明るく明るく" is not general ....
くよくよするなよ。元気だせ("be fine" with masculine way of talking) is more natural for me in Japanese.