“If a person desires, he may attain holiness as much at the setting of the sun as at its dawning,” Antonios the Great said, teaching his disciples thereby the power of repentance.”
Maybe I am mistaken, but I think this saying is quite straight forward. When we awake in the morning, we have yet to do anything we regret. By the time we go to bed, the day may be full of this or thats which we regret, must apologize, and ask forgiveness for.
Even if we live in solitude, interact with no one, we can still act or think in ways we regret.