I assure you that I did not post carelessly as I relayed what a knowledgeable priest told me. If a layman or an unorthodox priest told me anything, I wouldn’t have posted it.
I looked in my catechism and it says that voluntary occasions of sin are sinful and will *lead * to mortal sin, they aren’t mortal sins in themselves.
(First off - a layperson can give a perfectly orthodox and correct answer. They may even had a degree or degrees in Theology beyond that of a particular Priest…)
They are not the mortal sin themselves that “they are the near occasion of”- (*hence a near occasion of fornication is not the mortal sin of fornication) but they “can” be mortal sins “themselves” (a person for example who is morally certain that they will commit the sin of fornication of they do Z - and go ahead without necessity and with full knowledge and deliberate consent do Z - is a good example of a mortal sin".).
Occasions of sin…
There are all sorts of remote occasions of sin in life…all sorts of possible good things that one can do --where there is a possibility that some temptation may come.
Normally we are not “obliged” to avoid “remote” occasions of sin.
We simply cannot avoid all such things nor are we usually obliged to do so. We would have to knock ourselves unconscious…
What then is a “near” occasion of mortal sin that we are to avoid especially?
It is not simply temptation (though let us seek to avoid temptations).
A near occasion of mortal sin is such where one would generally falls into mortal sin -one generally commits a mortal sin (or even always!)–or is what is likely to cause one to commit a particular mortal sin now. Due to the nature of thing itself or ones particular personal weakness.
Though there can at times be good reasons to be in them…ones confessor can guide one or those that cannot be avoided (involuntary) (necessary occasions…which one still tries to make more remote…)
Those are the general principles for one to apply. Ones confessor can guide one. In specifics.
So can it be sinful to put oneself into a near occasion of mortal sin? Or remain in one? Yes. (it may be venial or even mortal or even not a sin depending on the reasons).
A clear example of when such would be a mortal sin could be -(with full knowledge and deliberate consent) when I am morally certain that if I put myself into circumstance Y that I will commit mortal sin Z. And I do so with that needed knowledge and consent.
*Ones confessor can advise. *