And I beseech you, brothers, let us stand upon our watch, because now is the time of soldiery. Let not our conversion be on the dunghill of this wretched body, but in the heart where Christ dwells. Let our conversion be on the judgment and counsel of reason, so that we do not rely so much on our conversion or lean on the fragile watch, but let us fix our position on the fortification, leaning with all our might on the most solid rock that is Christ, as it is written: He set my feet upon a rock and directed my steps. And so thus established and made firm, let us now contemplate in order to see what he might say to us and what we might answer to the one who accuses us.
The first step of contemplation is this beloved brothers, constantly to consider what the Lord wills and what pleases him, what is acceptable before him. Because in many things we all offend, and our crookedness offends against the rectitude of his will; our crooked wills cannot be joined or conformed to his will. ….. we no longer consider what is the will of God in us, but what is God’s will in itself. Since life is in his will, we do not doubt that everything that corresponds to his will is more useful and therefore more advantageous for us. And therefore, just as we anxiously wish to preserve the life of our souls, let us be equally anxious not to deviate from God’s will for as long as we can.
When we have made some progress in spiritual exercise, following the leader, the Spirit, who searches even the deep things of God, let us then ponder how sweet is the Lord, how good he is in himself, praying with the prophet that we may see the will of the Lord, and we may visit no longer our own hearts but his temple. And we will likewise say with the same prophet, My soul is troubled within myself; therefore will I remember you. That is to say, the whole summit of spiritual conversion dwells in these two: that when we consider ourselves we are troubled and saddened in a salutary way, and that in the divine, we enjoy rest and consolation from joy of the Holy Spirit. From considering ourselves comes fear and humility, from divine consolation we take up true hope and charity.
Bernard of Clairvaux, Monastic Sermons, Sermo 5: On the Words of Habakkuk 2:1: I will stand upon my watch (CF 68, p 38-39)