The longer a relationship lasts the more difficult it is to walk away. Many people see it as though they have "invested" too much time to simply let it go. However like any poor investment there comes a time when the smart thing to do is to stop investing in something that will never pay you dividends.
When we finally realize the person we are with will never become the person we "need or truly want" we must either learn to accept things as they are or leave in hopes of finding our ideal mate, The person that "gets us" and wants the same things we want out of life.
The hardest part of letting go is:
1. Breaking the news to your future ex,dealing with their reaction.
2. Starting over anew, allowing yourself to open your heart again.
One reason so many people stay in unfulfilling relationships is because they dread the idea of starting all over again. It takes more "courage" to fall in love a 2nd, 3rd, or 4th time than it does the first time. After a while they convince themselves there is nothing out there better than what they have and in fact things could be much worse. In other words the glass is half empty.