'Heartfelt' in the Bible

Be miserable and grieve and weep [over your sin]. Let your [foolish] laughter be turned to mourning and your [reckless] joy to gloom.

Therefore, confess your sins to one another [your false steps, your offenses], and pray for one another, that you may be healed and restored. The heartfelt and persistent prayer of a righteous man (believer) can accomplish much [when put into action and made effective by God—it is dynamic and can have tremendous power].