Confucious said that real knowledge is knowing the extent of one's ignorance.Aristotle and Socrates said the same thing.Is it a skill that can be taught or learned? It probably can, if you have enough of a stake riding on the outcome...
The beauty of life is, while we cannot undo what is done, we can see it, understand it, learn from it and change. So that every new moment is spent not in regret, guilt, fear or anger, but in wisdom, understanding and love.