You'll understand what life is if you think about the act of dying. When I die, how will I be different from the way I am right now? In the first moments after death, my body will be scarcely different in physical terms than it was in the last seconds of life, but I will no longer move, no longer sense, nor speak, nor feel, nor care. It's these things that are life. At that moment, the psyche takes flight in the last breath.
The moral virtues, then, are produced in us neither by nature nor against nature. Nature, indeed, prepares in us the ground for their reception, but their complete formation is the product of habit.
The life of theoretical philosophy is the best and happiest a man can lead. Few men are capable of it and then only intermittently. For the rest there is a second-best way of life, that of moral virtue and practical wisdom.