The stoic philosopher Lucius Annaeus Seneca the Younger has the distinction that more of his writings survived the test of time and is therefore a valuable primary source for stoic philosophy. 

Some of my favorite translated Seneca quotes:

• Luck is what happens when preparation meets opportunity.
• All cruelty springs from weakness.
• Religion is regarded by the common people as true, by the wise as false, and by rulers as useful.
• We suffer more often in imagination than in reality.
• If a man knows not to which port he sails, no wind is favorable.
• No man was ever wise by chance.
• Only time can heal what reason cannot.