Picasso isn't simply saying that creative people should ignore practicality—he's naming something subtler: the tyranny of the *already-known*, the weight of accumulated agreement about how things must be done. Good sense whispers that your idea won't work, that it contradicts precedent, that sensible people have already settled this question. A painter following only good sense will paint what everyone agrees paintings should look like; a parent following only good sense will raise children the way they've always been raised. The quote's real sting lies in recognizing that safety and consensus, those respectable virtues, are precisely what flatten originality into familiarity.