"But behold, and fear, and tremble before God, for ye ought to tremble; for the Lord redeemeth none such that rebel against him and die in their sins; yea, even all those that have perished in their sins ever since the world began, that have wilfully rebelled against God, that have known the commandments of God, and would not keep them; these are they that have no part in the first resurrection."
This is a good reminder to repent before we die in our sins... but it is more than that as well. :) When we know the truth, we have a responsibility to live it. This isn't to make our lives harder... I think that life is easier when you know the purpose of your existence. It's because we've tasted what God has in store... the infinite goodness of being able to return to him. We've caught glimpses, and been filled with that hope. If we turn our backs on something that we know, and refuse to repent, then we know exactly what choice we're making, and God isn't going to ameliorate the consequences for us. When we know the truth, we have to accept personal responsibility for the actions we take in relation to it... We know that we're here on Earth to improve. To get a body, to learn happiness, to learn to return to God. Let's work on improving rather than rebelling against our primary ally.