May be something related with what you asked - if one can design his/her life overwell , hope that’s would serve the larger purpose of life. and everyone is different and unique so ofcourse now question is how one should know. ans could be - read, observe, study & research from reliable sources , small experimant and reflect back , do divergent set of things, somehow get rid off deep social conditioning, by the way am reading a book - Design your Life by Bill Burnett
Self Introspection may be a key to find your purpose and passion. There very few blessed souls who can understand what is their purpose and passion in life and that comes from your soul searching. Sachin Tendulkar may be considered a blessed soul who found his passion early in the life and so his purpose. However, imagine a scenario if Sachin would not have been so successful in his career, whether you would still consider him that blessed soul? What about many other sportsmen who could not earn so much recognition, fame and money whether they had not found their passion and purpose? It is entirely on oneself to look internally to find her passion and purpose. Someone's purpose of life may be to be a good housewife, (remember our mothers from 20th century) they devoted their entire life in raising their kids and taking care of their families, did they not find their purpose or passion? You develop a sense of self evaluation and find what is it that motivates you or which matches with your skills and attitude and you invest your time and efforts in that area to find your passion. Having said all that, let me say about myself that my sole and ultimate purpose is to become the best version of myself!
Cal Newport, in his excellent book So Good They Can't Ignore You, talks about how "follow your passion" is usually bad advice. The more obsessed you are about finding your passion and only doing the thing you are passionate about, the more likely you are to become unhappy when you're not in a position where you "love" every minute of whatever you are doing. So what instead of passion? Cal Newport says you should be building a craftsman mindset.
The fact is that whatever you do can be meaningful provided you approach it right. Passion is something that you create by developing a high level of competence and skill in any field.
The purpose of your life is not going to be a bolt of lightning from the blue. We must create our purpose, and isn't that liberating? You ARE in fact free to create your own purpose.
When you focus on gaining rare and valuable skills (in the pursuit of becoming "so good they can't ignore you") you will also find your passion and purpose. It does not happen the other way round.