Stoic quotes

Here are a few Stoic quotes I came across recently that I like.

Consider that as the heaps of sand piled on one another hide the former sands, so in life the events that go before are soon covered by those that come after.
— Marcus Aurelius

The things you think about determine the quality of your mind.
— Marcus Aurelius

Nothing brings happiness unless it also brings calm; it is a bad sort of existence that is spent in apprehension.
— Seneca