Nostalgia is a basic human emotion
Kodak created a billion dollar industry by giving people a tool to feed their nostalgia. We don't take pictures because we want to know what we're seeing now... we already know that. We take pictures because it makes us feel good to know that years later, when nostalgia for that moment comes around, we'll be ready.
Marketers spend a lot of time on other emotions... joy, love, jealousy, insecurity, greed... but nostalgia gets overlooked. I think that's an opportunity.
Aside: when you're doing something important, like launching a big project, or a new company, or running some sort of campaign designed to change things, keep a scrapbook. Not a note book, a tool for writing down facts. A scrapbook. Include photos and quotes and clippings and events. Two reasons. First, you'll be glad later (I still have scrapbooks from some of my previous projects) and more important, because it will remind you that you're doing something important and that time is precious.