Please keep in mind the three requirements for mortal sin: grave matter, full knowledge, and full and free consent of the will. If any of these three requirements are missing, there is no mortal sin. Here is how the
Catechism of the Catholic Church puts it:
Mortal sin requires
full knowledge and
complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart do not diminish, but rather increase, the voluntary character of a sin ([
CCC 1859 (
Catechism of the Catholic Church - Paragraph # 1859); emphasis in original).
Deliberately missing Mass on Sunday without just cause is indeed grave matter (cf. [
CCC 2192 (
Catechism of the Catholic Church - Paragraph # 2192)), but only you can determine if you did not have just cause,
or if you did not have full knowledge and full and free consent of the will. While I cannot determine this for you, here are some considerations from your account to keep in mind:
You were extremely tired, both from the late hours and perhaps also from the emotional impact of seeing your son-in-law off to war.
You did not intend to miss Mass, as evidenced by the fact that you set your alarm and tried to get up.
You honestly believed that you could not go to another Mass later in the day. For the future, please keep in mind that you can fulfill your obligation later in the day at a non-English-speaking Mass, but in this instance you apparently simply did not realize that.
Given these considerations, it does not appear that you committed mortal sin; but, again, that is something only you can determine. If you need further help in discerning this, please speak to your confessor. Priests not only absolve sin but help us determine whether or not we have committed sin.
