That is actually a really useful, affirming thought exercise that I've done before. Simply take a nice present-day experience and run it through the "20 year ago nostalgia filter". Where all the boring/frustrating crap that surrounds the experience is forgotten, and just the good thing remains surrounded by the golden halo of nostalgia. It makes me appreciate the present experience more and dulls the "oh, life was so much nicer 10/20 years ago" nostalgia thing (it wasn't, it just seems that way).