If you cut yourself because of a mental illness – while you are getting help – is it a mortal sin? I also drink and can’t seem to stop. I go to confession almost on a daily basis but I feel my confessions are sacrilegious.
Mortal sin requires grave matter, full knowledge, and full and free consent of the will. If any of those elements is not present, there is not a mortal sin. Although deliberately abusing oneself through cutting or excessive drinking is grave matter, addiction can mitigate one’s ability to consent to the action. Since you are receiving help for your addictions, you are doing everything you can to address them.
So long as you confess with the intent of not committing such sins in the future, your confessions are not sacrilegious. All that is necessary is the intent of the will at the time the confession is made. However, I strongly urge you to ask your confessor for a referral to a spiritual director who has experience in helping penitents who suffer from scrupulosity and/or obsessive-compulsive disorders. Daily confession would be difficult even for someone not suffering from mental illness. (Most spiritual advisors counsel those with healthy consciences to go once a month.) For someone who does suffer from such illness, it can feed the obsessive-compulsiveness and become counter-productive to recovery. A confessor and/or spiritual director experienced in helping such individuals can help you determine a confession schedule that is suitable for your needs.
Understanding Scrupulosity by Fr. Thomas M. Santa, C.Ss.R.