why are we here?

one fine evening when i completed all my work and i was about to leave for the day, suddenly i heard a voice, and i was shocked to see my head of my domain calling me for help and i was for replacing the emptied water can. i went and helped him and he thanked me for helping it and started walking for my bus. when i was walking towards my bus i started thinking why should he had to do this work. because that is none of his job to refill the emptied can but still he did that. this incident made me to think the title of my blog"why are we here?". are we in this world doing the things which are being allocated to us and i asked a question myself "do we serve the purpose of god making us live in this earth?". i tried myself finding the answers all the nonsense which all arouses in my mind. but i am unable to find a solution for all the question which ever arises in my mind and i sometimes even question myself i am the only person to think like this or each and every on in the world have a same guilty feeling like i have.