Well-intended acts can have disastrous results, as in She tried to help by defending Dad's position and they haven't spoken since—the road to hell is paved with good intentions. This proverbial idiom probably derives from a similar statement by St. Bernard of Clairvaux about 1150, L'enfer est plein de bonnes volontés ou désirs (“Hell is full of good intentions or wishes”), and has been repeated ever since. [Late 1500s]

Merely intending to do good, without actually doing it, is of no value.