Have you ever had a day or weekend where you knew it was great, one of the best? Have you ever stopped to think about why it was so great? Of course, a part of it is circumstance - who you're with, what you're doing - but I think it's more than just that. There's something that makes these "best moments" just magical.
I think it's also because of how you act and how you feel. The best moments come when you stop thinking and overanalyzing. You just live in the moment. You don't question what you're doing or the consequences; you just do what you want to do. You don't worry about how other people are going to judge you and you don't judge yourself. The best days come when you act the most "you" and you know that who you're with will embrace that and love that "you" as well. The best moments are those days when life makes sense, even for just that moment.
You can't manufacture those best moment days. You can't make them happen. But when they do, I believe they happen for a reason and exactly when you need them. To maybe teach you that all is not lost. That you need to hold hope for your future. That everything you fight for and work so hard for is worth it.
Those are the days that stay with you forever. The days that are imprinted on your memory. The days that you fell in love with the world, and the world loved you back.