I like the saying " The meaning of life is to find your gifts, the purpose of life is to share them."

Your question implies you were "put here for a reason." This is not the case. You simply exist and you must define your own purpose, if you even want one. How about starting with your basic rights to Life, Liberty, and the Pursuit of Happiness? So just find your happiness. =]

I have struggled with this too. I read a lot of philosophy to help me with this. Included in that was observations with how human beings need a purpose which is why we invent religion. As a scientist I can think about needing purpose in terms of genetic survival. Probably the genes of people feeling a purpose have been favored. Life is hard and those feeling purpose are probably better at fighting for it. In reality there is no purpose and I have ultimately chosen to come to terms with that truth and live my life the way I want.