@Millshake01
It's not easy. I had to do this talk last year. In hindsight I wish I had dropped hints beforehand to say that I'm not happy in the marriage and haven't been for a long time. As it came as a complete shock to him. And my grown up kids. Everyone was stunned. Which made it all so very difficult. He's back in the house. We are trying to give the marriage one more try. But it's not happening, so sadly I have to do the talk once again.
Good luck. I know how hard this is.
@Millshake01
It was kind of similar for me. When I told my STBX I wanted to end our marriage (after 24 years) he was shocked. I was very unhappy for a very long time and I thought he knew it but apparently not. He has a very difficult personality and there was no arguing with him, I could never win any of our arguments so eventually I stopped and just kept it all inside, but eventually, could not take it any longer.
Some people say your partner deserves an explanation, especially if there is no abuse or anything major that happened, while they may be right, I think that you should just rip the bend aid and get straight to the point. These things are hard no matter what "the reasons" are and nothing will make it easier, the more you explain the more painfull it will get, so if I were you I would just go straight to the point and say, I am not happy in this relationship and do not think it is mend-able. This is what I did. You will be tempted to try to explain, later too, he will wonder, kids will wonder, people will, but I would say, do not do it. No matter what the reason is the bottom line is the same, you are not happy and you want out.
Same goes for kids, my therapist said, not to say too much to them especially as it may come out as "blaming", so just told them I was not happy, we tried to work things out but it did not work and want to separate from their father. They did not ask many questions, it all went much better then I though, for now anyway. Mine are grown kids, two adults and one teen.