If any one saith, that a man, who is born again and justified, is bound of faith to believe that he is assuredly in the number of the predestinate; let him be anathema.
The Council condemns the false notion that to be justified or born again “assuredly” identifies a man as having been predestined to heaven. It's untrue because men most certainly may lose their salvation—not as a consequence of any weakness or failure on God's part, but by their own choice to reject God. We’ll see this idea condemned again in another post coming soon (hopefully) so I won’t belabor it here. But because it’s simply not true that only the predestined receive justification, it is likewise false to assert (as the canon says) that—having been justified—a man may or must believe himself to be among the predestined.
By way of reminder of our task here: we’re primarily interested for now in whether there is anything in the Decree on Justification or the associated canons to suggest that the Council of Trent taught anything other than justification by grace alone. Hopefully it’s clear that this canon does not do so. The fact that we must consent to our justification doesn’t mean that we save ourselves.