There was a time when I thought being busier was somehow the key to being a better person. It's what society ingrained in me growing up. If I didn't have a half dozen errands, a few appointments, and roughly a billion projects on the go at a given time, then I was a lazy person.
I'm not sure when it clicked with me how stupid that mentality is, but once I realized that I could say no to some things and the rest didn't have to be perfect, my mental health improved so much.