Not often that you give someone your heart that they will keep good care of it and when they throw it down the very steep cliff on the rocks down below, it is like someone has hit you with a ton of bricks, or a massive truck carrying mammoth tree trunks. But when you gather the sense to collect the pieces of your shattered empire that you had imagined it is important to remind yourself that you worth a lot more, and if someone cannot see that then it is their own loss. The world is full of people and in them there will be at least one that will fully match your domain, make you feel special and take care of you. Who wont take you for granted and will understand what makes you tick.
Now to the question why does love hurt so much? It is the same reason why a knife would hurt if it is slashed through your hand. Or when you put your hand inside the door, when you close it. Even though it isnt flesh that sends the nerve signals to your brain, in this case it is your soul that is hurt and in many ways a broken bone takes time to heal, a broken heart also takes time. The feeling of hopelessness would soon disappear once you get over that person and then there will peace. But rest assured it is a temporary situation, which I am sure everyone in the world has gone through at least once in their lifetime. Any permanent solution to the problem will be a very foolish thing to do even though it may seem to be a very obvious solution.
The main thing to remember is that you are not the only one. Millions of hearts get broken every day, and it is not always men or not always women. Research suggests there are equal men and woman suffering the same way you are feeling at the moment. And before you start recalling what you did wrong or what you could do differently, you should realize that you are perfect and even though the person could not see that he/she will realize that soon enough and whether it be today, tomorrow and when they do it may as well be too late. But dont cry the river over it you are far better than this and deserve to be with someone who realizes that.