I can't find it now but yes there was a study done a few years ago that had one group of elderly people play and act like children, and another do some "serious

I can't find it now but yes there was a study done a few years ago that had one group of elderly people play and act like children, and another do some "serious" adult activity for some period of time, and afterwards they took some markers of aging, and found it significantly diminished in the play group. But I wonder what the aging effect of our obsession with control is. In other words, would playful thoughts motivated by a desire for control still net those results? (if indeed you can even be playful and controlling at the same time) Based on what I know about psychology, I doubt it. Motivations matter, and letting go and accepting things as they are is one of the most psychologically healthy things we are capable of doing. I doubt if any of those yogis who achieved long life (if indeed they did) did so intentionally for the purpose of achieving a long life. Instead, it was likely a by-product - as so many of the best things are.