Can smile then why not smile?  
Joy can be then why not let it be?  
You can giggle out loud as well 
Then, why not do it?  
This much joy can be so please do smile 
Do not be sad since I do not enjoy seeing you unhappy 
My joy is in you 
Although, now you do not belong to me 
I can smile because my heart knows you are happy without me 
That is simply enough for me.
Rohit Sapra
http://www.poemhunter.com/poem/please-do-smile/