The enemy of our salvation especially strives to draw our heart and mind away from God when we are about to serve Him, and endeavors to adulterously attach our heart to something irrelevant. Be always, every moment, with God, especially when you pray to Him. If you are inconstant, you will fall away from life, and will cast yourself into sorrow and straitness.
True joy is the joy of consolation, the joy that wells up in the knowledge of one's own weakness and the Lord's mercy, and that does not need the bared teeth of laughter to express itself.
According to the degree to which the intellect is stripped of the passions, the Holy Spirit initiates the intellect into the mysteries of the age to be.
Fear God and keep His commandments both in your feelings and in your intellect. If you force yourself to keep them in your intellect, bit by bit you will attain to fulfilling them in your feelings.