A word of encouragement to those of you who are already separated. Don't lose hope. Although there are certainly challenges, many people do decide to move back in together after they've been separated. Whether or not this happens may depend in part with how you handle the separation.
Whatever you do, don't panic and chase your spouse. That will be a one-way street. Get help. Pull back. Work on yourself for a while and make yourself strong, someone your spouse may want to come home to. Learn about yourself and relationships during this crisis.
Then in the end, if your spouse refuses, at least you can know in your heart that you have done everything to save your marriage and family (if you have children).