Can a man never attain to that higheror lower, which is it?altitude of strifeless, unregretful hardness?
Something of extreme youth clings to his books—its zestfulness, curiosity, indiscriminateness, and its unregretful volatility.
1640s, "full of regret," from regret + -ful. Regretfully, properly "with regret," incorrectly used in place of regrettably "it is to be regretted that; calling for regret" since at least 1965. "A regrettable use, prob. after HOPEFULLY adv.2" [OED].