Sounds like you have some understanding of grieving, and hopefully you will move through this process towards that peace of mind that you need. Do you already know about the possible stages (denial, anger, bargaining, depression, acceptance, etc.). Perhaps try to realize what was unhealthy about the relationship, while appreciating any positive aspects. And allow yourself some time to settle your mind. Realize what you could not change. And plan for moving forward. You will get through this.