Actions birth consequences, regardless of whether we think of them as such. The repercussions of our actions(or inactions) always back fire accordingly, sometimes in the form of regret for something we've done to ourselves or someone in the past.
Regret is a double egded sword depending on how we choose to view it. Since the feeling of regret is birthed from mistake, it won't be far fetched to say that we all have things we regret doing (or not doing) since we all make mistakes and since regret only comes once we've realised our mistake, there's this pain that comes with it, especially if things go so wrong that there's no means to correct the damage that has been done.
We do things with ourselves that end up affecting us in the long run and then we regret our actions, we can still work to correct it when we realise our mistakes and the more we do the work, although after a delayed realisation, we end up feeling better, since it involves us alone. Example is when we regret all the times wasted in procrastination during our old days, but then decide to make amends by becoming productive. This type of regret are birthed from actions that involves mostly us and is more easy to dispel by forgiving yourself and striving to do better.
The greater form of regret comes from actions and mistakes that involves a third party, like when we hurt a person really terribly but being blind to that fact at the time of our bad attitudes, they leave or something else happen along the line that makes us comes back to our senses and then we regret. The thing with this form of regret is that, it is very hard to do away with especially when the attempts we make towards making things right with those we've trespassed against become in vain, like when they can't find a place in their hearts to forgive us or even say things that they otherwise wouldn't have said to us and when the bond keeps getting weaker and weaker until the point where it is no longer there, we go down the "had-I-Known" road. Now this point is very critical because that road of regret we take can soon become an abyss if care is not taken, taking us deeper and deeper into the depths of the pain of regret. It reaches a point where due to how deep we're in regret, we become blind to other things that could make us see the bright side of life again, leading us into depression and we end up doing more harm than we've done to that person, to ourselves.
The pain of regret, being the double edge sword that it is, can be used to better ourselves instead of letting it draw us into feelings of self hate. That pain can be a reminder never to repeat the mistakes we did that caused hurt to others and generally improve our state of well-being when we truly learn from that mistakes. We are bound to make mistakes as human beings and why repetitive mistakes can be a sign that we're trying to be better, one has to be careful if the mistake affects others so this type of mistakes shouldn't be repeated often and we should try our best to take as much lessons we can take from the first one as possible.
Do not drown in the river of regrets, whether or not the mistakes were intentional or not, as long as you truly regret your actions with all sincerity, which means you would try to avoid such mistakes in the future, then I guess that's all you need to move on.
Thanks for reading.