The morning meditation consists of being grateful for the new day when you wake up. You take a few moments to compose yourself and then think about your plans for the day ahead, imagining how you can make yourself a better person,
while also accepting that some events are beyond your control.
The evening mediation involves a daily retrospective where you think about what you did well during the course of the day, and also reflect on what you could have done better. The aim is personal growth and intentional cultivation of the four Stoic virtues: moderation, courage, fairness, and wisdom.
The Stoics reflective practice probably derived from the earlier Pythagorean school. Not much of Pythagoras' writings survived antiquity, since the school was destroyed by an angry mob, and Pythagoras himself may have been murdered.
What we do know about the Pythagoreans is that like the Stoics, they believed in the protective virtue of moderation, and that a person who wants to grow will naturally align themselves with the good.
This excellent Youtube video by the scholar Manly P. Hall, gives a great overview of the surviving Pythagorean fragments, entitled the Golden Verses of Pythagoras: