I think there are various possible factors going on - certainly fear of failure, certainly a resistance to authoritarianism/the spectre of being told what to do (especially if that has been figural in one's early life), creating false drama by leaving things until the last minute to alleviate a sense of boredom, etc.
And also, as you say, a misunderstanding of the emotional or other load that the task will take, which is probably a habit that has an interrogable history.