Just a very thoughtful question.
why is it so hard for one to break up with someone that they really love? what is your reasoning?

Your heart is both fragile and strong. It is strong in love, but it is easily broken. Its hard to break up with them because your love for them, your bond to them, is strong and they mean the world to you. Its like you're taking your own world from you. You're ripping away the part of you that you love the most; Them. The worst part about it though, Is that you're the one who is making the choice and you know it will kill them just as much as you. However, If it is absolutely best for both of you, It must be done. Im sorry you're going through this. If you need someone to talk to, you can talk to me if you need to. Good luck!