The only sort of tasks worth being set were impossible ones.

Everything is theoretically impossible, until it is done. One could write a history of science in reverse by assembling the solemn pronouncements of highest authority about what could not be done and could never happen.

Everything is theoretically impossible, until it’s done. One could write a history of science in reverse by assembling the solemn pronouncements of highest authority about what could not be done and could never happen.

Only the impossible is worth attempting. In everything else one is sure to fail.

There are many things that seem impossible only so long as one does not attempt them.

Every noble work is at first impossible.

We may, indeed, set it down as an absolute certainty, that many things are erroneously deemed impossible; for, till we know all the possible—and how far we are from that need not be insisted on—how can we know what is impossible?

The only impossible thing is something to be impossible.

Nothing in this world is worth having or worth doing unless it means effort, pain, difficulty.

Anything new, anything worth doing, can't be recognized.

Nothing worth doing ever, ever, ever came easy.

The moment one gets into the ‘expert’ state of mind a great number of things become impossible.

what was over couldn't be begun, and what couldn't be cured must be endured;

If a thing is not worth doing, it is not worth doing well.