"Did you have a good day?"

answer: "I had a great day today!"
means "I got in a great workout today, and a bunch of other stuff got done, too!"

answer: "It was a pretty good day."
means "My day actually went to heck, but I got a workout in."

answer: "Today was alright."
means "I blew off my workout, and I wasn't feeling guilty for it until just now when it is way too late."

answer: "Today was a waste."
means "I had to participate in real life rather than going for a run and now I'm feeling sorry for myself."

There. Now you know.