As with much anything else, it probably depends on the person. I think it's only natural to think about your exes, especially if you were with them for longer periods of time. I know I certainly think of mine every now and then, but it's mostly in the context of "Wow, I'm so much better off now" or something of that nature.
Mind you, there's a pretty big difference between healthy thoughts of one's past, and outright obsession. If you find yourself with someone and constantly obsessing over an ex, you might want to consider spending some time alone to sort that all out.
But if it's just a passing thought every now and then, I'd chalk it up to some good ol' reminiscin'. And I certainly don't seem anything wrong with that.
I think BruinDan is right in saying it depends on the person (although I havn't seen an advocate or sepert be wrong yet). But I don't agree with the quote you gave. It may take only a second to like someone, but I think it takes longer than a day to love someone(I'm not love-at-first-sight person.) I think we need to get to know the person deeply before we can love that person. But I agree slightly with the part that says it takes a lifetime to forget them. Maybe not a lifetime but a long time. I have not forgot one of my exes, but I live a small town and none of them have moved away(unfortunate in some of the more abusive cases,as they still try to torment me).
But thet's my little speil about that for now.
"I don't wanna be you" -Good Charlotte from "the Anthem" "Who I am is who I want to be" -Reba MacIntire
Copyright 1998, 2014 Heather Corinna/Scarleteen
Scarleteen.com: Providing comprehensive sex education online to teens and young adults worldwide since 1998
Information on this site is provided for educational purposes. It is not meant to and cannot substitute for advice or care provided by an in-person medical professional. The information contained herein is not meant to be used to diagnose or treat a health problem or disease, or for prescribing any medication. You should always consult your own healthcare provider if you have a health problem or medical condition.