The positive thinker is a hard-headed, tough-minded, and factual realist. He sees all the difficulties clearly. . . which is more than can be said for the average negative thinker. But he sees more than difficulties - he tries to see the solutions of those difficulties.
You attain aptness by judging while in good shape and in a good situation (good light, good distance, etc. ), through the exercise of good barn-sorting epistemic competence.