@leaky20 You're absolutely correct when you say "purpose is subjective", but then without any purpose, no matter what it is to you, it's difficult to measure progress. As I said earlier, the meaning of purpose need not be as profound as some motivational articles tell us. It need not be directed towards changing the entire world.
Everyone needs a purpose to live. We, all unknowingly give ourselves a purpose to fulfill. For example, providing for one's family as a father, is a purpose ingrained in most of us. But, we might not explicitly run these thoughts in our heads(As in "I am a father, and hence I must provide". It's implied for the most part.) What you mean is perhaps "higher purpose", which is not a necessity, but then it is what makes champions. Finding one's higher purpose and much less pursuing it, almost never is "all sunshines and rainbows", which is why it's easier to ignore them. Happiness is an incentive, a byproduct of fulfulling a purpose. Some of us find happiness in simplest things. For some of us, we need much more. But then again, those who chase higher purpose, don't do its solely for themselves. It can be said that fulfilling a higher purpose, is permanent and when considering the totality of every lives one might touch in their pursuit, the rewards are higher.