Please note that it doesn’t „hurt” you that you did not do something in the past, but that you regret it now. This feeling of regret or even anger has its place in your body.
You will not change the past, because it simply does not exist anymore, but you can change what you feel in relation to the past, because these feelings appear in the body, and the body is always present in here and now.
I will try to explain it as short as possible and suggest some action.
If there is a thought about a past event, you have his mental image, image and feeling that this image in your body evokes.Once again: thought appears under the influence of unaware processes that I am not talking about here. Let go of investigating now, why the thought appears at all.
So you have an image (image) and a feeling (a physical reaction in the body).The mechanism seems to be a simple – action (image) and reaction (feeling).The thought process consists in the fact that whenever you think about it (the image), the same reaction appears in the body – the feeling.
In the best case, you will repeat this process many times and finally your reaction will become weaker (the sensation will not be felt in the body – only the picture will remain in the memory). In this case, it is often said: time heals wounds. The memory (picture) will become „indifferent”, that is, it will not excited emotion. I remind you that we work with unwanted, destructive feelings.
Now a different way.
When an image from the past appears and evoke a reaction in the body. Leave this picture, do not play the movie again from the beginning, and again. Pay attention to the feeling that is in the body.
When you locate it (remember, do not follow the image that will appear), focus your attention on the place where accumulates this feeling (eg clenched throat, chest, abdomen).
When all your attention is in this place, focused on this feeling – Stop here, take a deep breath, keep the focus on the feeling in the body and slowly release the air, inhale … and repeat this process until the body is clearly relaxed in the place where this sensation occurred. It will dissolve like fog.
Check how it works, the exercise doesn’t last long. The whole idea is that „time heals wounds” to replace „presence dissolves pain.”