The one thing I don't remember mentioned is the opposite effect (but maybe I missed it) - if you experienced a failure to accomplish something, the free will explanation is likely to make you stop investigating the root cause, leaving it as a mystery.

Only to straw-man libertarians, who think their decisions emerge out of nowhere. Real libertarians accpet that their decisions are influenced, but not to the extent of complete determiniation, and so might well be motivated to tweak the influences.