In this quote, Cicero is referring to old age as the last of life, but also as a masterpiece. He is acknowledging that life resembles a play with various acts, and aging is the last act - one that ought to be valued and valued. The phrase "crown of life" recommends that old age is a time to be pleased with, a time when we have actually achieved and accomplished what we set out to, and we can wear our accomplishments with self-respect. Cicero motivates us to commemorate the end of our play, and to accept the knowledge and experience that features aging, instead of fearing it.
"Tomorrow is the most important thing in life. Comes into us at midnight very clean. It's perfect when it arrives and it puts itself in our hands. It hopes we've learned something from yesterday"