How to find your purpose and passion in life?

I was conducting a study sometime ago as to the feasibility of a certain endeavor when I came across a YouTube video; and in it, a particular quote- a Mark Twain's quote which I must have since referenced at least a dozen times in my conversations: "the two most important days in your life are the day you are born and the day you find out why". How loud those words resonated in my mind; and even now, still resonate