Prayer for Leading a Holy Life:
St. Thomas Aquinas (1225-1274)

Grant, O merciful God, that I may ardently desire, carefully examine, truly know, and perfectly fulfill those things that are pleasing to you, to the praise and glory of your holy name. Direct my course, O my God, that I may do what you require me to do. Show me the way and grant that I may follow it as is necessary and profitable to my soul.
Grant to me, O Lord my God, that I may not be found wanting in prosperity; that I may not be lifted up by one nor cast down by the other. May I find joy in nothing but what leads to you; sorrow in nothing but what leads away from you. May I seek to please no one, nor fear to displease any. May I fear only you. May I despise all transitory things, O Lord, and treasure all things that are eternal. Let me loath all delights without you, nor desire anything apart from you. Let me find pleasure in all toil that is for you; and weariness in all rest where you are not.
Grant to me, O my God, that I may turn my heart to you always, and grieve for my failings with a firm purpose of amendment. Make me, O Lord, obedient without opposition; poor without repining; chaste without blemish; patient without murmur; humble without pretence; merry without riotousness; serious without heaviness; cheerful without frivolity; God-fearing without abjectness; truthful without duplicity; doing good without presumption; correcting my neighbour without pride; edifying him by word and example without hypocrisy.
Grant to me, O Lord God, a vigilant heart that no subtle speculation may ever lead me from you; a nobleness that no unworthy affection may draw from you; a rectitude that no evil purpose may turn from you. Grant me a steadfastness which no tribulation may shatter; a freedom that no violent affection may overthrow. Give me, O Lord my God, a mind to know you, diligence to seek you, wisdom to find you. Give me a way of life pleasing to you, perseverance to trust and await you, and finally faith to embrace you.
Grant that my punishment may be averted through penance here; your benefits used in this life through your grace; that your joys may be enjoyed in heaven in glory. Who lives and reigns, one God forever and ever.  Amen.