I believe you can love someone more than anything in the world. This is even if they don't and wont ever love you in the same way. They can have no idea how much you love them and you will continue to love them even then. It's not something that is futile,it's a love that you will never give someone else,a love that you will never feel for someone other than them. You will love another and be completely happy with them,but always love that one person in a different way. Not a painful love,not a disappointment,just a love like no other.
