Compendium of the Catechism:
vatican.va/archive/compendium_ccc/documents/archive_2005_compendium-ccc_en.html
- When does one commit a mortal sin?
1855-1861
1874
One commits a mortal sin when there are simultaneously present: grave matter, full knowledge, and deliberate consent. This sin destroys charity in us, deprives us of sanctifying grace, and, if unrepented, leads us to the eternal death of hell. It can be forgiven in the ordinary way by means of the sacraments of Baptism and of Penance or Reconciliation.
- When does one commit a venial sin?
1862-1864
1875
One commits a venial sin, which is essentially different from a mortal sin, when the matter involved is less serious or, even if it is grave, when full knowledge or complete consent are absent. Venial sin does not break the covenant with God but it weakens charity and manifests a disordered affection for created goods. It impedes the progress of a soul in the exercise of the virtues and in the practice of moral good. It merits temporal punishment which purifies.
It is of course difficult for a person here on the forum to tell you if you committed a mortal sin or not…and yes you are correct that a confessor can help you…
But it is important to note that in order to commit a mortal sin …there has to be grave matter (yes lustful thoughts/pleasure is grave matter) and full knowledge and complete consent. Even if a temptation comes back when we try to set it aside (fleeing is the best way)…this does not mean one has committed a mortal sin…for one needs full consent.
So the main question for yourself when tempted… is “did I give full consent”(deliberate consent).
(of course …one should note too there is a difference between some thoughts etc “happening to us” and our say…going and doing something we know will be a near occasion etc and one can sin by putting themselves willingly in them (for example a person knows he ordinarily gets drunk (looses completely his reason) when he goees to a particular bar…so he should avoid that bar)…so we do need to very much avoid the near occasion of mortal sin…but without scruple…)
This too can help:
The classic stages of temptation when we are tempted are:
- Suggestion (the evil is proposed to us in some way) this can be quite attractive …can be thoughts that happen, ideas etc.
- Pleasure (a kind of automatic pleasure can happen from the suggestion) this pleasure can just happen…one is not “trying to have it” not wanting it…this is just a reaction.
3…then one either consents or does not consent.
(one can either consent fully and thus engage in things willingly …or not consent and perhaps thus grow in virtue…following Christ!)
Now it can also often happen that one begins to “partially consent” but then rejects it and thus does not give full consent.
When one is tempted…
Some signs that one lacked consent or gave only “partial consent”:
If even though there was some instinctive pleasure …we do not want it…we are unhappy or horrified about the evil…or struggle to not be overcome …we turn to God in Prayer --these are some signs of no consent (if of course we stay in this stage…and do not later consent)
(For example some thoughts come out of the blue just cause one happened to see an attractive person…and one does not want the thoughts but turns to God in Prayer or is horrified by them and turns to something else etc…no matter how much they come back…if one does not consent at all…there is no sin…but rather possibly growth in virtues)
If one hesitates for a moment but then does not want to sin and so rejects it and does not give full consent (thus a fault against prudence)
If one resists but the resistance is half hearted…one does resist but it is weak or slow…but in the end one rejects it…such would seem to be half consent and thus venial
Of course if one then gives in and gives full consent…then such can be mortal…remember…partial consent or half consent is not full consent…and thus not mortal.
In the end …if there is still doubt that one consented:
if the person is lax (they do not see many things as sin for example …basically they are lax…) …one can urge confession for it is likely they consented otherwise it would not bother them…
for the delicate conscience or the scrupulous or one with scruples…one can rule out full consent for if they would have fully consented…it can be said that would know it.
(Based on A Tanquery… the Spiritual Life…and he bases things on S. Augustine…but much of this is simply repeated in various places…for it is the basics in judging such)
So…this may help in your examine.