When the 'purpose of life' as a question appears, the first answer I hear is 'to find happiness' and in one point I agree. But what if....
we came to Earth to have the greatest adventure to experience life in Human form.
Just think about it. Your Soul incarnated to a physical body just like a space suit and entered to this Earth through the womb of your mother.
You would say the purpose of life is to find happiness, but happiness is the place where you came from, from the forever bliss, where your soul is in perfect balance and peace.
What if you came here to understand time, to understand the whole spectrum of feelings. In that aspect, this is the greatest opportunity to find out how to control your physical and mental body through several experiences which all of them (good and bad) were given to you as a gift to master your skills to become the observer and the ruler of the emotions, feelings and thoughts.
The moment you master it, may you find happiness, but you also will have a container or Grail if you like, to hold all kind of emotions, thoughts in your possession and use it at your command.
And when you are truly mastered to be in an observer position, in your 'happy' or 'bliss' state while in Human form, may you manage to put all your life experiences in a line and find a theme, the key behind it, a certain kind of Divine Order, a special meaning for it all. And that moment, you will truly understand what your life purpose is... to becoming the One, you destined to be.