I am not sure that’s true. Angels, we are told, are creatures of pure intellect, whose wills are entirely united with their intellects; never at war with their reason as is the case with us. If so, then the fallen angels saw with absolute clarity the choice they were making, yet made it against God. In doing so, their choice was made irrevocable, not because God would not forgive them, but because that’s the way angels exercise choice. It is difficult for us to understand something like that, because we are torn all the time between what we know we ought to do and what we will to do and what we actually do. We do not understand with perfect clarity. It is almost impossible for us to imagine a deliberate choice made against union with God for all eternity, and particularly one made by a creature so brilliant that, as one commentator said “if we perceived an angel as it truly is, we would be absolutely convinced that it was God”. It could be reasonably surmised that at the point of choice, there were but two choices; union with God or union only with the angel’s own self. Heaven, then, might rightly be seen as a “mode of being”, i.e., in a union with God that we cannot fully understand but which angels understood. Being “tossed from heaven” (Christ put it as a “fall”, being more descriptive of an active separation than a passive separation, like a man letting go of a trapeze) could simply be a change in the “mode of being”. Possibly that change is from a willing union with God to a willing disunion. It seems impossible for us for a smart thing like an angel to willingly separate itself from God, but then, we see smart people do the same thing all the time. Heaven is the eternal contemplation of God; implying a “tapping into” the infinite knowledge, love, happiness and wisdom of God; a resource we can never exhaust. But if angels knew that, how could they give it up in order to contemplate only themselves for all eternity? Perhaps precisely because they did not want a “mode of being” that was dependant on another being, however much greater it is than themselves. Again, that seems incredible. But St. Therese of Lisieux believed that all souls get a shot at Final Penitence, but that those who “volunteer” for hell do so out of a love for themselves so intense that the very idea of forever declaring dependence on God is repulsive. At that moment, such souls declare for the hell of self-love and self-contemplation for all eternity, knowing full well the consequences of that declaration. Hard to picture in a way, but if a person thinks about it long and hard, one can see it; a pride so overwhelming that, to borrow from Milton, it chooses to reign in the hell of its own limitations than to serve in the heaven of a Being upon whom we will always be dependent for our happiness.
So, I am not sure the fallen angels regret their choice, or would go back. They have chosen a way to be, knowing exactly what it was. As their wills are perfectly united to their intellects, one of whose attributes is decision-making, they “never change their minds” because they never WANT to change their minds.
It is not impossible to imagine that we are “like God” in a way different from the way in which angels are “like God”. In this life, we are drawn toward God. We might resist that drawing force, or we might accept it, but we are drawn nevertheless, in a way analogous to the way the Son loves the Father and the Father the Son. Unlike angels, then, in this life we are incapable of truly and irrevocably making the “non-God” choice in the same sort of way the Son cannot reject the Father or the Father the Son. At a point then, if St. Therese is correct, we are capable of seeing the choice clearly and making it irrevocably. After that, we never change our minds.
I do not pretend to be a theologian, but it’s fascinating to think about all of this.
Sorry.