Life without purpose makes little sense and is unlikely to yield long-term happiness. It is like taking a step forward and then two steps back. Without purpose we may be busy, but end up not accomplish much.
We should not postpone thinking about our purpose because later may be too late. Time passes in one direction and you can’t simply press reset and start over. You only have one shot to live your life well. You don’t want to wake up one day to find out you wasted your life, do you?
Many people have various goals in life that they call “purpose”, but purpose is higher level than goals. Goals stem from a purpose. Most religions propose or even instill some purpose of life, but such purpose is based on belief and therefore cannot be justified by facts and logic.
The natural rational purpose of life of any living organism including human is sustainable survival and humans are no different. Survival has three horizons. In the short horizon, instinct guide our own survival. In the mid-horizon, we have children to ensure survival of our genes and memes. And in long-horizon, we need to ensure our next generations can survive. Long survival horizon requires long-term priorities which conflict with our incentives and therefore is the most endangered.