Wow----why did I feel great today and finally at peace?

I can't comprehend it. I have never had any peace in my life and it was like my problems and anger and desperation anxiety lifted. I could not sleep last night and had a full day today, beginning with seeing a new family doctor. I have never felt so at peace in my life. However days ago I was in a fit of rage and breaking things and wanting to hurt myself. I had so much guilt and anxiety and anger that i could barely breathe. I have no idea what gave me this peaceful state of mimd without the constant erflies and that dirty feeling in my chest and my dark thoughts were gone. I am not on any meds or anything. THis is the best day I have had since I can ever remember. I truly felt at peace for one day in my life. I don't know how to keep it up or what it even means. Any thoughts?