I don't know the content of the day 149 word story, so I can't tell its main idea.
As we have no access to the 'day 149 word story' itself, it's impossible to determine its main idea. It could be centered around a moral lesson, a character's journey, or an event. But without reading it, we're in the dark.
Since we lack the actual text of the 'day 149 word story', it's hard to pinpoint the main idea. If it's a fictional story, it might be about love, friendship, or a struggle against an antagonist. If it's non - fictional, it could be about a personal discovery or a social issue. But all of this is just speculation without seeing the story.