I would have to say "a good day" is relative to what is important in your own life. There are a number of things that contribute to what I would consider a good day for me.
Most of my days start out with a good hug with my wife. If at the end of the day we are still smiling and enjoy each other's company, a good day!
If I have the opportunity to get in some sort of physical exercise before I go into work or even on the weekend, a good day!
I I accomplish something at work that I consider worthwhile for me and the company I work for, a good day!
If I run into an old friend and spend time in a good conversation or I meet a new friend and we have a good discussion, a good day!
If I have a conversation with my son, a good day!
If I have the opportunity to help someone out, a good day!
If I fix something that's broken, a good day!
If I eat well and don't feel guilty about it, a good day!
If I get the opportunity to stop by and visit my Mom, a good day!
If I learn or experience something new, a good day!
If I get in touch with my higher self, a good day!
How 'bout you, what's your criteria for a good day?