In search of Serenity!!!

My Life keeps on surprising me. I was searching for serenity, doing yoga, pooja, walks and what not . But still mind is not calm, its in search of something, is it serenity or my aim in life. Why am i born.. What is that purpose for which god made me.. There might be some work which has to be done by me, and could be done only by me.
God has decided something for each one of us, and we all keep on searching for that "what". What for, are we made for? What is the Real aim of our lives. If I'll get the answer to this question, "what is the purpose of my life?" my search of serenity will be complete.