The Metaphysics of Morals by Immanuel Kant Chapter 1 Page 7

beneficent cause, but not that it should subject its desires to that weak and delusive guidance and meddle bunglingly with the purpose of nature. In a word, nature would have taken care that reason should not break forth into practical exercise, nor have the presumption, with its weak insight, to think out for itself the plan of happiness, and of the means of attaining it.

Nature would not only have taken on herself the choice of the ends, but also of the means, and with wise foresight would have entrusted both to instinct.

And, in fact, we find that the more a cultivated reason applies itself with deliberate purpose to the enjoyment of life and happiness, so much the more does the man fail of true satisfaction. And from this circumstance there arises in many, if they are candid enough