I wish I could take back the biggest mistake of my life, getting married.
why you think like  this? regret is a negative conscious and emotional reaction
Regret
yes, regret is related to perceived opportunity
Because it cost me a lot of headaches and a ton of money.
the negative emotional experience relating to a loss outcome both similar neuronal correlates
That is a good way to look at it. But I still wish I had a time machine to go back.
oh!full feedback occurs  and with disappointment partial  feedback
Trust me, it is a very negative experience.
negative emotion predicated on an upward, self-focused, counterfactual inference". Another definition is "an aversive emotional state elicited by a discrepancy in the outcome values of chosen vs. unchosen actions".
Regret differs from remorse in that people can regret things beyond their control, but remorse indicates a sense of responsibility for the situation. For example, a person can feel regret that people die during natural disasters, but cannot feel remorse for that situation. However, a person who intentionally harms someone should feel remorse for
Regret
Regret is a negative conscious and emotional reaction to an undesirable situation. 
Regret is related to perceived opportunity. Its intensity varies over time after the decision, in regard to action versus inaction, and in regard to self-control at a particular age. The self-recrimination which comes with regret is thought to spur corrective action and adaptation. 
In Western societies adults have the highest regrets regarding choices of their education. 
Definition.
Regret has been defined by psychologists in the late 1990s as a "