I did this and split with the man I had been with for 9 years. Nothing wrong with him, as santa said, life was safe and easy but we had been together so long it was a case of either marrying him or leaving him. I just couldn't marry him so I knew I had to let him go. There was nothing wrong with hi, good provider, kind, good in the house. It was like living with a flatmate though, I didn't want to be intimate with him anymore. I had tried breaking up with him a couple of years earlier but I had wavered and he had seen that and seized on it. He refused to leave and I ended up sticking it for a couple more years. When I finally did it again I was much firmer and made sure he knew I was serious and this was it, no going back. This time he left immediately after I told him and moved back in with his parents. You have to let him know that you mean it. After he left I broke down and sobbed and felt absolutely bereft but I would never have let him see me like that as I didn't want to give him any idea that he could win me back.
I convinced myself that I was his world, he had no friends, no life, would never find anyone else, was condemning him to be sad and lonely. Utter nonsense. He had convinced himself that I was his world, I was his first serious girlfriend so it wasn't that he couldn't be with anyone else, he just couldn't imagine it. I genuinely thought he would be on his own for a while and I would be ruining his life
[arrogant]
When I did split with him he played all sorts of nasty tricks and really wore me down trying to get me back. It was horrible but I stayed firm and felt such relief it was over.
Within 2 months he had met someone else and almost 4 years on he is married to her and thankfully we have no contact at all. He clearly did find someone else who made him much happier and treats him as he deserves.
Don't convince yourself he couldn't manage without you, you are doing both him and yourself a great disservice. He will get over it and you will both probably be happier. It is horrible at first but if you stick to your guns you will both work it out. You both deserve to be happy and he can't be happy with someone who deep down, doesn't want to be with him.