Simplify the following text for a Grade 10 native English-speaking person.
Original: Marcus Aurelius ' work Meditations , written in Greek while on campaign between 170 and 180 , is still revered as a literary monument to a philosophy of service and duty , describing how to find and preserve equanimity in the midst of conflict by following nature as a source of guidance and inspiration .
Simplified: Marcus Aurelius ' work Meditations , written in Greek while on campaign between 170 and 180 , is still revered .