Obviously Catholicism doesn't teach certainty of salvation officially, so no comments about how much better Reformed theology makes people feel are necessary (universalism is even more comforting). But I figured I'd put up 2 quotes from St. Alphonsus Liguori (probably the most hated doctor of the Catholic Church by Protestants, because of his book "the Glories of Mary") on assurance. In any case, here are 2 thoughts on assurance from this great Roman thinker:
"[On 2 Peter 3:9, "He is patient with you, not wishing that any should perish but that all should come to repentance."]...From all this can you now have any doubt that God wishes to save you? From this moment onward never dare to utter again: "I wonder does God wish to save me. Maybe He wishes to see me damned on account of the sins I have committed against Him." Get rid of all such thoughts, once and for all, since you must now realize that God is helping you with His graces and calling you insistently to love Him."
"The Lord is full of goodness to those who seek Him. No one has ever trusted in the Lord and been rejected."
To read more, check out : http://thedivinemercy.org/news/story.php?NID=3280
St. Alphonsus Liguori, Ora Pro Nobis.