Congrats on taking this big step.

Of course it is sad, even when we logically know it is in everyone's best interest for the relationship to end, doing it is really sad. We don't go into this with the hopes of ending it... .
Yes, he will make this difficult, but stay the course. Also, make sure to brush up on communication tools from staying, your right approach can help make things not get totally out of hand. When I was able to apply them, those tools did work.
Peace,
SB