It was my little dream to own 21 BTC and today i achieved it after hard work of so long time.Now i want to make my hard work pay me.I mean,i want that these bitcoins work for me someway and grow.Is there bitcoin bank that pays interest? What will you do with 21 BTC? How will you spend it? How will you grow it? Share anything you want that may help me to decide what should i do. 
I think that I would hold on to them and get at least a bit more and it is also going to depend on what the value of the Bitcoin is at that moment. If I am happy with the money that I can make then I would sell them.