To represent God as requiring impossibilities on pain of eternal damnation is to hold God's character and government to unbelievable reproach and ridicule. People know intuitively that any government that requires natural impossibilities is unjust and its governor is nothing but a cruel tyrant. Impossibilities are not commanded by God. And if His commands are possible, then we must be able to obey. Thus, we are able not to sin.
Love is the willing of the highest good according to the value of the object loved.
Therefore to love God any less than supremely is to really not love Him at all. The obvious answer is yes. Now since love is the fulfillment of the law, if we are able to love God and our neighbor, then we must conclude that we are able to obey the law of God. And if we are able to obey then we are able not to disobey, hence we are able not to sin. To believe that we are unable to fully obey the commandments of God is to say that it is impossible to obey them.