Most people would be very happy if their worst problem in life was thinking it could have been more mentally stimulating. People have regret on their deathbed because people don't want to die and wish they could have their cake and eat it too, not because they suddenly found wisdom.
Anecdotal but I had a lot of people dying around me stating they spent too much time chasing money and too little on living. And I know a lot of pensioners as well who say the same thing; now they are living the life they wanted but have little time left (they think; I always come up with statistics and say they have 20-30 years more but he, who listens to that?). Another salient detail; most guys say they shouldn't have had kids because it took away too much time and most women reget not having more. Anecdotal, still, two countries and around 100 people. Research papers were written with less :)
