ever so slightly different...
"Those who are the hardest to love...need it the most."
The heart has reasons that reason does not understand. (Possibly by Jacques-Benigne Bossuet who lived from 1627 to 1704). Very similar to the quote attributed to Blaise Pascal (1623-1662): "Le coeur a ses raisons que la raison ne connait point", or "The heart has its reasons which reason know not of". Wise saying anyway :)