"Life is a process, not an event." Another common saying that means essentially the same thing is "life is a marathon, not a sprint." This means that life is not a simple task to be checked off the to do list. Instead, it is a long, complicated affair that you work on and adapt to constantly over a long period of time. Another way to think of it is that an event is usually a singular event with a definitive start time and end time, like a concert or a class. A process is more of a long term commitment that is composed of numerous steps that you do not simply autopilot through but instead actively work on. In other words, a process could be thought of as a long series of different events. And while life certainly has a start point (birth) and an end point (death), we do not know how long our lives will be nor do we know what will happen to us, so we have to be prepared to adapt to the different stages of life and the various events that will happen to us over the course of a lifetime.
The perfect example of this is raising children. Caring for an infant is very different from caring for a teenager or having a relationship with an adult child. Yet all are part of the process of life for a parent.