Responsiveness to regret was specifically reduced in successful aging paralleled by autonomic and frontostriatal characteristics indicating adaptive shifts in emotion regulation. Our results suggest that disengagement from regret reflects a critical resilience factor for emotional health in older age.
They continue:
The experience of regret is elicited by counterfactual thoughts, that is, comparing “what is” with “what could have been.” Thus, regret is typically induced by presenting people not only with the actual outcomes of their choices but also with missed opportunities (i.e., alternative outcomes that could have been obtained had the choice been different). The influence of missed opportunities on future choices can be regarded as an indicator of regret responsiveness.
Thus it appears that "no regrets" is a good life style. It is always interesting to examine these types of studies. For there may be very good people who regret not doing more and outright evil folks who have no conscience. It appears that that element is not considered.