Every single day is a good day to have a good day :)
Though there are seasons in our lives where it seems as though having a good day isn't possible, we must grab hold to the attitude that every day can be a good day if we attempt to make it one. Just because things may not have been going the way that you would like them to in a day, doesn't mean that you can't make a good day out of it.
Turning your negative thoughts into positive thoughts will ultimately turn your actions in positive actions as well. Seek inspiration from sources that will leave you inspired, put yourself around people who try to make every day as positive as possible, and stop wasting energy complaining when you can instead make things better. Every day is a great day to have a great day, never let your circumstances, or environment get you down.