And on the morning of the third day, he said, “Ugh.”

三日坊主
mi-.kka.bou.zu

Literally: three – day – priest – master

Alternately: Giving up on something after only trying it out for a little while. Alternately, someone who has trouble sticking with their projects over the long term. Literally, a “three-day priest.”

Notes: The “three days” part is supposed to represent a short span of time rather than a specific measure. More interesting, though, is the term bouzu: as the individual character meanings imply, it originally referred to the head of a group of (Buddhist) priests. Over time, it came to refer to such priests in general in a somewhat intimate or mocking way. Eventually, this was further applied to boys, for whom a (monk-like) very close haircut had become common after the importation of clippers and the banning of traditional topknots during the Meiji era.

First day? Both images apparently from a mobile game called [南無三！やる気が水の泡]

Third day – eyebrow-power has subsided and the third eye is sleepy.