You've probably heard the saying "you can't change the past".
But, I disagree. That statement is somewhat dis-empowering, and I'm all for the empowering stuff!
You can't change actual events that happened in your past, but you can absolutely change your perception of those events. YOU get to choose what something means, and in turn how it makes you feel.
You see, everything you experience in life is in itself neutral. It is our own perception that labels our experiences good or bad, happy or sad, in accordance with our beliefs.
When a situation causes you pain, it is a sign that something is 'off' in your inner world. When this happens, it's a chance to look at the underlying negative belief and take charge of it and therefore understand how this belief impacted your perception of the situation.
You can change the past