Don't you every start wondering, what if I could take back my mistakes made in life? The smallest detail could mean the biggest thing if you allow it to unfold
well regrets are percieved to missed opportunities, so if it relates to that then yes
Without regret then we could never learn from our mistakes. For some it is much more harsh than other.
intensity varied over time for decisions so you maybe you will come around  
Hopefully I do and then I will be able to realize what regret rally entitles
in the west ironically the highest regret is where people go for their education
Yes that it extremely unfortunate,  me being witness to many close individuals who have experienced that.
but remember Regret is distinct from disappointment and both have similar nuerolocigal effects
You are very right but disappointment does not only let you down but also entitles other factors. 
professionally defined by psychologists in the late 1990´s as a "negative emotion predicated on an upward, self-focused, counterfactual inference".