A smile is the simplest form of rejoicing in the Lord.  In the Bible there are several words that are all translated rejoice.  In the original language they mean everything from spin around with great energy, let out a loud sound, to simply brighten up.  

I recently did an experiment of simply choosing to smile even though my emotions did not feel like smiling.   I was amazed at how a simple smile changed the entire atmosphere around me.   Even when I am home alone, everything changes when I smile.  

So rejoice in the Lord today.... choose to put a smile on your face!