FEAR OF THE KID’S REACTION:
Every parent wants their child to grow up in an as emotionally stable environment as is possible for you to create. Sometimes the act of creating stability actually requires you to separate from the person with whom you believed you'd raise those children.
As a child of divorce, I can tell you that not only are children generally resilient through a divorce when their parents have gotten on the same page and have agreed to be emotionally supportive of them, most children prefer their parents being divorced and happy than married and miserable. If you do what is necessary as co-parents to be the backbone and support that your children need, you and they will get through this process together. In fact, the children may even be healthier for you having done so.