we should not care about what we want because that leads too instinctive.
we should not consume coca cola or fast food, a katana in the chest is a quicker way to die
The man in the church says our purpose is to please the creator.
The lady in the science lab says our purpose is to find out how it all works.
The philosopher says our purpose in life is to give life a purpose.
Nature says our purpose is to reproduce and continue our species.
To me, the purpose is to find joy, conquer fear, live morally, make a difference in the world, help others, and then be proud and happy when it all ends and live on in the memories of my friends and family. In the long run nothing you or I do will matter though so just chill and enjoy your time.
The way I go about this? Every day in my choices I try to do things that work towards those goals. If, when I lie in bed at night and look back on what I did that day with pride, then I know I'm doing well. If not then tomorrow's a new day and I get another shot at it.