Would someone be kind enough to explain the "love thy enemies" concept?

Granny simply can't wrap her head around it. I've been sending up a slew of imprecatory prayers aimed at my yardman, Fernando, ever since he slammed the back door, causing my chocolate cake to fall! How can I love him when he ruined one of my beautiful cakes? I may need two fingers of my home-brewed tonic to help me get past this conundrum! Help me, Jesus!