Does it do a person any good to pray while he/she is in a state of mortal sin, since mortal sins cut people off from God’s grace?
Definitely not! NEVER STOP PRAYING! If you have committed a mortal sin, repent and make a perfect act of contrition. A perfect act of contrition is to express sorrow for to God having offended Him and the desire to amend one’s life. When one has the first opportunity to go to Confession, one ought to do so. The moment one is truly sorry for having sinned, one is forgiven. But knowing the genuineness of one’s sorrow is difficult to ascertain. So with the sacrament we know for sure that we have been forgiven. Nevertheless, the sooner we ask forgiveness, the better.
Fr. Vincent Serpa, O.P.