I agree with Sexyeyes.
One of the biggest mistakes I made in my last breakup was trying to make myself be over him just because the relationship was over and I "shouldn't" care anymore. Fighting my overwhelming grief and disappointment only prolonged the process. Too many people repeated the "Just move on"/"There's somebody better out there"/"You'll be fine"/"Just focus on other things" mantras when what I really needed to hear was that it is completely fine for me to be sad, to cry, and to feel a little misplaced.
I had to discover on my own that a broken heart heals at its own pace. Every relationship will not be the same and will not have the same impact on you and therefore you will not be "over it" in the same length of time.
I would say I spent a little more in depth recovery time on this last breakup because it did impact me in a major way but also because I was determined to learn all I could from the experience...about him, about me, and about the dynamic between us. I squeezed the juice out of it, and now I feel so much better for it.
So, I agree that oftentimes, revisiting the situation is not always the best course of action, and I tend to be an all or none type of person when it comes to those types of things...but I do know that there are exceptions, and I realize now that just because you take a little longer to process the breakup doesn't mean something is wrong with you or that you should rush or that you want to get back with him. It may mean that a profound work is being done in you that will serve to strengthen you and present you impeccably prepared for the next opportunity before you. It happened to me and now that there's a new guy I'm considering, I'm actually glad that I took my time and moped and processed the grief. I'm stronger and wiser for it.