[logicallee]

Well, you can already deduce one fact regarding your question from OP: a 30-day challenge that brings its user a clear and obvious benefit does not work (at least, we know it does not work 100% of the time) as a way to introduce and stick with a productive and positive habit, even where the burden of that habit is low.

Some other way, different from a "30-day challenge" must be used to introduce the habit, because this method does not work (or at least does not work 100% of the time).