Why slowly? Won't that just hurt more by dragging it out?
You have to realize from the start 99% of the people you will be with won't be the one you will be with forever. If the person you are with doesn't bring out the best in you and the inverse isn't true than that person is someone who you shouldn't be with. By slowly dragging things out you are wasting yours and the other person's time. The best is to break it off in no uncertain terms and make no promises of friendship. If your relationship was meat to be, it would have been.
Are you as dumb as I look?
It can be hard to let go of a person that you have been with that long, even though you know for sure you do not see yourself with them in the future or you see your future going badly if you stay, you just have to have a long talk with them and let them know that you want to move on. IT may take time to really have it be over but once you take the first step you will feel better. There may be some rough times when you feel like just going back to the relationship but stay strong and get what you want and deserve.