Achieving a superhuman level of efficiency, so that you never need to disappoint anyone, or make tough choices about how to use your time? Impossible. Satisfying the contradictory demands of maddening bosses (or family members) who can’t decide what they want? Impossible. Bringing a creative project into the world precisely as you envisaged it in advance? Impossible.
Not just “really difficult” – which leaves open the thought that with a bit more self-discipline and the right techniques, you might manage it – but literally impossible, like making two and two add up to five, or jumping two miles in the air. Which is a liberating thing to realise, because you get to stop beating yourself up for failing (why would you beat yourself up for failing to jump two miles in the air?), and focus on something doable instead.