(A little late on this: taken from this excellent article on the Saint by my sister, which I recommend you read)
Lord God almighty,
open wide the door of my heart
and illumine it with the grace of the Holy Spirit,
that I may seek what is pleasing to your will.
Guide my thoughts and my heart,
and lead my life in the way of your commandments,
that I may always seek to fulfill them,
and that I may grasp the eternal joys of the heavenly life;
through Jesus Christ our Lord.