ことわざ kotowaza: proverb or saying
Today, I was reminded of a proverb:
「三日坊主」 mikka bouzu
literal meaning: a monk/priest for 3 days
What it really means is someone who seems enthusiastic about something at first, but then cannot stick with it for more than 3 days. Like someone who suddenly decides to be religiously devout, but then after 2 days of trying to be a Buddhist priest/monk they give up or lose interest by the 3rd day. So it is often used to describe people who give up on things easily. I cannot think of a really equivalent English phrase at the moment. Maybe faint of heart or fickle are somewhat close.