Letters 20.4

And I can tell you, further, whence arise this unsteadiness and disagreement of action and purpose; it is because no man resolves upon what he wishes, and, even if he has done so, he does not persist in it, but jumps the track; not only does he change, but he returns and slips back to the conduct which he has abandoned and abjured.

Seneca, Letters to Lucilius 20.4, translated by Richard Mott Gummere