I think the hardest kind of break-up is a mutual break-up.
When you both know that you are supposed to be together, but there are factors beyond your control that don't let you be. The sad part about marriage is that it is important to be practical too. Simply being in love isn't enough.
Sometimes, no matter how much you both love each other, you know that marriage isn't an option. Those break-ups hurt the most.
When it is not the fault of any of the people, but of the situations and circumstances. They are the worst because you know you will always love that person no matter what. But you also know that getting married would have spoilt the relationship that you both have.
You still want to stay in each other's lives, so you remain friends, without the romantic part. You secretly cry because you wonder why life is so unfair.
Sometimes it's simply a case of meeting the right person at the wrong time. Or maybe the time would never be right for you both.
You remember all the good moments you both had together and all the future dreams you had. Life was simpler when we were younger and didn't have to be practical and logical. When you could just dream without thinking realistically. When we only listened to our heart and not to our mind.
Sometimes, it's simply a case of the heart not being able to accept what the mind already knows. You know that you both could not be together anymore, but your heart refuses to listen.