Earthly suffering, when accepted with love, is like a bitter kernel containing the seed of new life, the treasure of divine glory to be given man in eternity. ... Those who suffer in union with Him already experience in this life a joy that can seem humanly inexplicable.

Heaven in fact begins on earth, beatitude is anticipated in the Beatitudes. 'In holy people,' Saint Thomas Aquinas said, 'there is a beginning of future happiness.' (STh I-II q69 a2)

(Pope John Paul II, Address on the Mystery of the Church, 1994)