Obstacles to Prayer

Επιθυμῶν προσεύξασθι ὡς δεῖ, μὴ λυπήσῃς ψυχὴν, ει δὲ μήγε, εἰς μάτην τρέχεις. Ἄφες σου τὸ δῶρον φησὶν ἐμπροσθεν τοῦ θυσιαστηρίου καὶ ἀπελθὼν πρότερον διαλλάγηθι τῷ ἀδελφῷ σου, καὶ τότε προσεύξῃ ἀτάράχως. Ἡ γὰρ μνησικακία ἀμαυροῖ τὸ ἡγεμονικὸν τοῦ προσευχομένου καὶ σκοτίζει τούτου τὰς προσευχάς. Οἱ λύπας καὶ μνησικακίας ἑαυτοῖς σωρεύοντες, καὶ προσεύχεσθαι δοκοῦντες, ὅμοιοί εἰσι τοῖς ὕδωρ ἀντλοῦσι, καὶ εἰς τετρημένον πίθον βάλλουσιν. Ἐὰν ὑπομονητικὸς ᾖς, ἀεὶ μετἀ χαρᾶς προσεύξῃ. Εὐάγριος ὁ Ποντικός, Περι προσευχῆς

Desiring to pray as you should, do not grieve any soul lest you run in vain.  Leave your gift, it says, before the altar, and first go away and be reconciled to your brother, and then pray without disturbance. For the memory of evil blinds the leading faculty of him who prays, and darkens his prayers. Those who heap up sorrow and memory of evil within themselves, and expect to pray, are like people who draw water and pour it into a wine jar that has holes in it. If you are able to endure, you will always pray with joy. Evagrius Ponticus, On Prayer