Meditations 8.47

If thou art pained by any external thing, it is not this thing that disturbs thee, but thy own judgment about it. And it is in thy power to wipe out this judgment now. But if anything in thy own disposition gives thee pain, who hinders thee from correcting thy opinion? And even if thou art pained because thou art not doing some particular thing which seems to thee to be right, why dost thou not rather act than complain?—But some insuperable obstacle is in the way?—Do not be grieved then, for the cause of its not being done depends not on thee.—But it is not worth while to live, if this cannot be done.—Take thy departure then from life contentedly, just as he dies who is in full activity, and well pleased too with the things which are obstacles.

Marcus Aurelius, Meditations 8.47, translated by George Long

When thou art vexed at some external cross, it is not the thing itself that troubles thee, but thy judgment on it. And this thou canst annul in a moment. But if thou art vexed at something in thine own character, who can prevent thee from rectifying the principle that is to blame? So also if thou art vexed at not undertaking that which seems to thee a sound act, why not rather undertake it than be vexed? But there is a lion in the path! Be not vexed then, for the blame of inaction rests not with thee. But life is not worth living, this left undone. Depart then from life, dying with the same kindly feelings as he who effects his purpose, and accepting with a good grace the obstacles that thwart thee.

Marcus Aurelius, Meditations 8.47, translated by C. R. Haines