Have you seized? Yet a little exertion is needed after the seizure, that what you have seized may not be taken from you. If we run on, if we look to none of those things that are set before our eyes, if we consider nothing but how we may escape from those who would hinder us, we shall be able to retain with all security what we have seized. Have you seized on chastity? Tarry not; flee beyond the reach of the devil. If he sees that he cannot overtake you, he will cease to pursue; as we, when we can no longer see those who have robbed us, despair of the pursuit, and do not pursue, nor call on others to stop thief, but suffer them to escape. So do thou run vigorously at the beginning, and when you are beyond the reach of the devil, he will not afterwards attack you, but you will be in safety, securely enjoying those unspeakable blessings, which God grant that we may all obtain through Jesus Christ our Lord. To whom with the Father, and the Holy Ghost, be glory, power, honor, and worship, now and for ever, and world without end. Amen.
Source: Homilies on Second Timothy (New Advent)