The end of any relationship is difficult, whether you've spent years together or just a few months. Love isn't put to rest overnight and can linger long after you've said goodbye. Some experts say it takes half as long as the relationship lasted to process it and move on. Others say grief holds itself unaccountable and to no specific timetable, that it can go on for months and years. Rather than the duration of your time spent with each other, it is the quality, the intensity, of this time that will dictate the length and breadth of grief. A few shorts weeks with a woman you felt a true connection with might be much harder to get over than a man you liked and were with for years, but never quite meshed with. Both relationships might've been viable at one time, yet both led to the same place anyway - saying goodbye. And it is in the parting (yes, parting is such sweet sorrow. Or, sometimes, parting is such sweet relief!) where you can begin again. Except of course if you aren't really ready to say goodbye.
Breakups can be brutal, on both sides. Usually, because of a shared history and strong emotional connections, the one leaving doesn't want to hurt the one being left, and the one being left doesn't want to be let go. Those early, pure feelings of desire, which brought you two together, become tangled up in ego, in resentment and pride and the need for self-protection. You close up and off. You turn away from what you admired and respected in the other, because it's just too damn painful to see it and know that it wasn't enough, that in the end you just "weren't feeling it."
If you are the one leaving, be kind. Make the end as clean and clear as possible. Or, as a good friend of mine says, "Be sure to use a sharpened machete, not a rusty butter knife." If you cut it off, make sure that it stays off. There's nothing worse than a wishy-washy breakup. If this is what you really want, then be strong in your convictions, because the other will go on hoping against hope that you'll eventually wake up and change your mind, that you'll see what you're missing and come back around. Sometimes, you will, only to leave again. Sometimes, you won't, and regret it.
If you are the one being left, be kind to yourself. Everyone will tell you not to take it personally and you shouldn't. Try to separate your wounded ego from the reality of the situation - that for whatever reason, this other person simply didn't want what you wanted at the exact same time. I hate to reduce good, productive relationships down to timing, but more often than not, timing is all we really have to go on. If he wasn't in the right place in his life, there's nothing you could've done to change that. Patience might win out in the end, but then again, so does resentment. You can only wait around so long for someone to get his act together before you realize that "getting his act together" is just an act and that you deserve far more than this.
Do not make someone a priority, if he only makes you an option. And that goes for the grief you will feel as well. Try to contain it. Let it preoccupy you less and less each day. Give it a few minutes and stick to those minutes. Remove old photos, erase voice messages, cards, trinkets, any object that reminds you of him or her. At least for now. Later, much later, you might look back fondly on what was, but right now, you've got to let go of what isn't. If it's a nice day, go fly a kite, take a walk on the beach, look at some art. Find what makes you happy again, because that's who she fell in love with to begin with. And that's who you are anyway, even if you can't see yourself clearly through the tears. But you will. You will.