You know what I realized?
This may seem obvious, but even when you have a bad day, it's not good to go to bed upset. The idea that, "Well, tomorrow will be better" is a nice one, but why can't today end off well, too? I think you should be happy about having lived each day of your life, even if there are things that happened that day that weren't amazing. I think it would be nice to try and find at least one good thing that happened, or to do something at the end of the day that makes you feel good. I don't mean to be selfish, I mean to try and be happy.
Each of our days is a gift and I don't think we are meant to dismiss days as solely bad, or as a waste of a day. Even if you do waste time, it's good to do at least one productive thing per day, to do at least one thing for someone else, to do at least one thing that makes you feel good about yourself.
Not every day has to be the best day ever. In fact, if every day was, amazing days would become routine and then they wouldn't be special. But each day should still make you feel happy or fulfilled in some small way. You should go to bed at the end of it and be able to say, "Today mattered."