What makes the human brain fascinating is our ability to learn from everyday experiences and have the option to better ourselves. Due to the organic nature of the brain, our brains constantly re-wire and prune unused neural connections in effort to keep cognitive functions that are truly necessary for our everyday use while “losing” neural circuits we no longer need. This is exactly what is happening at a neurological level when we find ourselves “rusty” in a language we haven’t used in years. Our brains assume we no longer have use for the language due to lack of use, and it prunes those connections it deems unnecessary to “make room” for more relevant stuff.
The human brain also experiences the emotion of regret because the act of regretting welcomes reflection on what we should have done in a particular situation. By feeling regret, we are able to perhaps make a better decision the next time we are faced in a similar situation. What about computers, will they ever be able to function on a human level? Google is interested in answering that question.