When I was 19 years old I sent a mental message to the older me. The message said I should never look back on this time and assume that the happiness I recalled was a product of nostalgia or "rose tinted spectacles", I really was having a good time. The message continues to come through.
@marcusgreen I did the opposite at 18, so that I wouldn't make the mistake in later life of looking back on the "happiest days of my life". It was purgatory, if not hell.