Three words that go in front of the verb and colour how something came about — understand them by ear here. ดัน says it happened when it should not have and the speaker is annoyed ("he went and told her"), or with no subject blames the circumstances ("of all days, it rained"); อุตส่าห์ means "went to all that trouble", and what comes next is the disappointment; เผลอ means you did it without meaning to.