“When a man receives something Divine, in his heart he rejoices; but when he receives something diabolic, he is disturbed. The Christian heart, when it has received something Divine, does not demand anything else in order to convince it that this is precisely from the Lord; but by that very effect it is convinced that this is heavenly, for it senses within itself spiritual fruits: love, joy, peace, and the rest (cf. Gal. 5:22).”
— St. Seraphim of Sarov, Little Russian Philokalia: Vol. I