You’ll have to forgive my memory, but I believe in Humanae Vitae Paul VI spoke of the “contraceptive mentality” that can indeed be had by those using NFP.
An act obtains its morality from its object, and both intentions and circumstances form part of that object. That is, what is it you are aiming at in performing a sex act using NFP? What are you aiming at in using ABC? What are the circumstances surrounding the act?
Personally, I think the object changes in the two cases, although it can be the same. Using ABC, the intention is to not have a child, but it requires no respect for the personhood of the partner, which is a difference in circumstance and de facto a change in object. If I can have sex with my wife without respect for her, then I am going to demand it often; many times without respecting her. She becomes an object of my concupiscence, not a human being in the fullest sense.
Furthermore, there is no maintaining of the mean of temperance when using ABC’s. This I think, is the main crux of the matter. With NFP, there is an attempt at virtue, which ultimately has a view to the common good of the marriage. With ABC’s, self-indulgence is rampant, and thus, for lack of a better term, the objectification of partners.
My wife and I at one time contracepted, and believe me, at times it was more about self-satisfaction than about my wife. I didn’t need to respect her, or even court her, because I knew that sex could be, or should be, had whenever I wanted. I definitely lacked the virtue of temperance (and still do, though things are getting better

.
Using NFP, the object can be the same as with ABC’s. If a couple’s intention is to use it so as to never have children, or with a contraceptive mentality, the object of that act is the same as using ABC’s. However, in the majority of cases, the cirumstance is changed by the bringing in of the virtue of temperance.
Furthermore, on the psychological level, I think NFP couples are more open to life because there is an
openness to the possibility of error. With ABC’s, I think the case is different. THe possibility of error is not considered, and so the child is de facto, if conceived, a problem rather than a blessing.
Finally, I’ve found that in using NFP, during the fertile times, I have to court my wife because sex is off limits. Behold, the Romance is still alive!
Is it hard during fertility? Certainly, but I like the challenge. For Aquinas and Aristotle, the virtuous man is the happy man. Believe me, at fertile times in the past I’ve thought they must be wrong because the urge was that strong; however, it has gotten easier to refrain because the
habitus has been formed. Alas! Sex doesn’t control me (as much) anymore; I control it!