He would be guilty of mortal sin, because he exposes himself to the danger of grievously offending God. Hence, before he acts he must lay aside the doubt; and if he has not hitherto done so, he must confess it, at least, as it is before God. But the scrupulous, who have doubts about everything, must follow another rule: they must obey their confessor. When he tells them to conquer their doubts, and to act against scruples, they should obey with exactness; otherwise they will render themselves unable and unfit to perform any spiritual exercise.
Alphonsus LiguoriWithout prayer it is impossible to resist temptations and to keep the commandments.
Alphonsus LiguoriA person may be Baptized, and yet not born again to grace, in consequence of not having the necessary dispositions at Baptism.
Alphonsus LiguoriBefore the coming of Jesus Christ, men fled away from God and, being attached to the earth, refused to unite themselves to their Creator. But the loving God has drawn them to Himself by the bonds of love, as He promised by the prophet Osee [Hosea]: "I will draw them with the cords of Adam, with the bonds of love" (11:4). These bonds are the benefits, the lights, the calls to His love, the promises of Paradise which He makes to us, but above all, the gift which He has bestowed upon us of Jesus Christ in the Sacrifice of the Cross and in the Sacrament of the Altar.
Alphonsus LiguoriSaint Teresa, as the Roman Rota attests, never fell into any mortal sin; but still Our Lord showed her the place prepared for her in Hell; not because she deserved Hell, but because, had she not risen from the state of lukewarmness in which she lived, she would in the end have lost the grace of God and been damned.
Alphonsus Liguori