Well until science evolves sufficiently it can only really be a psychological principle. All the things you refer to help towards making someone feel good about themselves which often gives them a youthful verve to their emotions, outlook and perceptions.
But ageing (until the scientific breakthrough we are all waiting for) is an irreversible process and whilst we can dress ourselves up to achieve the above, we are still getting old. You can keep an 18th Century Chippendale cabinet looking �as new� for many many years (250 years probably!) and although quite handsome, it has some history and is still old.