We must reckon with the possibility that something in the nature of the sexual instinct itself is unfavorable to the realization of complete satisfaction.
Sigmund FreudMen are not gentle, friendly creatures wishing for love, who simply defend themselves if they are attacked, but ... a powerful measure of desire for aggression had to be reckoned as part of their instinctual endowment.
Sigmund FreudAs regards intellectual work it remains a fact, indeed, that great decisions in the realm of thought and momentous discoveries and solutions of problems are only possible to an individual, working in solitude.
Sigmund Freud