As a Christian, I need to train my heart, because:

The world has a lot of influence!  It wants us to be squeezed into its mold.

We still deal with the remains of sin.  Standard behaviors, stock responses – we need to learn new habitual reactions.

A well-trained heart glorifies God – and that's ultimately what we want to do.

"Dear God, please give me a love for those unlovely – help me see people not through these earthly eyes, but through Christ's.  ~Amen"