The problem is, trying to figure out our life purpose can be tricky - I think its a bit harsh to say "The only mistake is not knowing your purpose." With this ideology people rush into things for the sake of finding a purpose. Its like trying to meditate; by trying to force it youre missing the point to begin with!
Good post, but I would say take your time, enjoy yourself and be grateful for everything around you. Sometimes the best ideas for what we want to do in life come when we least expect them.