16 Great is the Baptism that lies before you: a ransom to captives; a remission of offenses; a death of sin; a new-birth of the soul; a garment of light; a holy indissoluble seal; a chariot to heaven; the delight of Paradise; a welcome into the kingdom; the gift of adoption! But there is a serpent by the wayside watching those who pass by: beware lest he bite you with unbelief. He sees so many receiving salvation, and is seeking whom he may devour. You are coming in unto the Father of Spirits, but you are going past that serpent.
How then may you pass him? Have your feet shod with the preparation of the gospel of peace; that even if he bite, he may not hurt you. Have faith in-dwelling, stedfast hope, a strong sandal, that you may pass the enemy, and enter the presence of your Lord. Prepare your own heart for reception of doctrine, for fellowship in holy mysteries. Pray more frequently, that God may make you worthy of the heavenly and immortal mysteries. Cease not day nor night: but when sleep is banished from your eyes, then let your mind be free for prayer.
And if you find any shameful thought rise up in your mind, turn to meditation upon Judgment to remind you of Salvation. Give your mind wholly to study, that it may forget base things. If you find any one saying to you, Are you then going in, to descend into the water? Has the city just now no baths? Take notice that it is the dragon of the sea who is laying these plots against you. Attend not to the lips of the talker, but to God who works in you. Guard your own soul, that thou be not ensnared, to the end that abiding in hope you may become an heir of everlasting salvation.
Source: Catechetical Lectures (New Advent)