Maggie-
The cows have left the building and the water has gone under the bridge. The things of the past are unalterable. There are many things that none of us can control. Just look at all the lunatics on the road.
You may have not handled things perfectly. Well, welcome to the club. There are many things that I look back on and say, "Damn! I should have done this or that or the other." Yes, I should have, but I didn't. So do I beat myself up about it? At times. And then I try to get a firm grip on reality. I can't change it. I must embrace it and learn from it. Forgive yourself first.
So, how is the best way to discharge the emotions tied into these events. You need to find a counselor or a small group. I am tempted to say a trusted friend, altho I feel that I may be bordering on the oxymoronic. If you have someone you can confide in and know what you say will go no further, count yourself as blessed. By talking about this- meaning how hurt and angry you are, how sad you are, what ever you are feeling- not a recitation of the incident itself, it will cease to have such a strong hold on you.
You say that you love your new job. Maybe GOD allowed this to happen to put you in a better place than you were.
JayR