The sudden absence of your partner creates a hole in your life. If the relationship has been going downhill for a while, or even felt emotionally abusive at times, there may be a sense of relief, but after a period of days or weeks, loneliness is likely to set in. There is not another body filling your space, someone to bounce off of even if the other person said little or even nothing at all. The sense of you suddenly being only with you can have a powerful impact.
But loneliness, whether it comes in spurts on a long weekend, or whether it is a chronic undertow dragging down your life; is a natural consequence of any ending. It comes with grief; and grief, that sense of loss, comes regardless of the quality of any relationship. It's about psychological attachments that are suddenly cut off.
Joining this Support Group will allow you to connect with others who have gone through the same situations and may have found different ways to deal with this issue that you may find useful. It's always good to have someone else to bounce ideas off and in this Support Group you will find the means to do that.