I would like to mention the difference between realities. We have conventional reality and ultimate reality.
Conventional reality is based on concepts such as "I, Me, Self, Persons, things, entities, animals etc." Here there is a Self, an experiencing entity, a creator of kamma.
In ultimate reality there is no concepts, meaning that there is no I or Self. In other words there is noone to blame or to restrain.
Regarding the past. What have been done have been done. Pondering about it is not conduceive to ones practice. Reacting to these mental formations only serve to bring one away from the Present moment and into delusion.
Remorse, regret of the past, thinking about what could have been done differently belongs to the 4th hindrance, ie. Restlessness and Worry. The hindrances are what keeps on from developing in meditation. You can read more about them here.
Lastly, in buddhism we try to develop a non-stick mind. A mind that does not cling or have aversion. We practice non-reaction, non-interfering with phenomena. Instead we observe them and learn from them. We observe phenomena and let them show us their true nature. When reacting to them, e.g. reacting to emotions we provide them further fuel to burn. We strengthen them. Its like taking a magnifying glass and concentrating the sun rays. They get stronger. In the same way if we have aversion towards them they also become stronger and grow bigger.
When just observing phenomena without interfering they are not being provided any fuel. Instead we turn them into objects of observation. We make them into the soil that will nurture our spiritual growth. So when these mental formations arise you can observe them and note them (Mahasi Sayadaw Tradition) in order to realize their impermanence, unsatisfactoriness and uncontrollable nature, i.e. the 3 signs of existence.