If you can make up what your measure of success is, you can control how successful you feel. I have had moments where taking a shower and going for a walk exceeded my measure of a successful day. Other days, I've felt like I haven't succeeded because I didn't magically know something that I had no experience in and beat myself up for looking stupid or ignorant.
The trick I am trying to master is setting a measure that's attainable but also promotes some growth. Being someone who either holds themselves to an absurd standard or allows themselves to be extremely idle makes this balance pretty hard.