Often people say you will find a better person, actually it is better if it is not.
After a romantic rejection, a well meaning friend suggests us to get over this person and you will find someone better. Our heart doesn't like this thought of someone better than what it chose.
An important realization is that somethings will never be with us, no matter how hard we try. The thought that we would find someone better is a way of telling ourselves you can overcome the present rejection with some object better (perceivably) than this. This thinking is fundamentally flawed in that you are discounting your own emotions and judgements. You are trying to escape the humility required to mourn the present loss forever.
You will most certainly find someone different but it won't be the same person our heart once so longed for. Process this, what our heart wanted a while ago, could not be found. It won't be in future either. And you can do nothing about it.
Rejection gives the humility required to be a decent human being who can understand the value of love. It may or may not be hard, but it certainly is different and unique -- often it is something you don't really understand.
You ask yourself a thousand times, "why?". You cry at the odd hours into the night, reliving the memory. But, once again there is nothing you can do about it.