You do not need a god-given purpose to create change in the lives of yourself and others. In fact, being free of a deterministic destiny means that your actions are more meaningful, because they were the result of your own personal choices, instead of some unchanging pre-determined fate.
You're begging the obvious. Looking for meaning is a trait human ancestors evolved throughout millions of years to survive. That's why a healthy adult is always driven by a goal. The Universe doesn't "think", why would you believe that random chance was acting in a grand scheme of things.