Why is loving others often so difficult?

Stop faking affection for them. The biblical truth about loving difficult people requires something entirely different than generating warm emotions. True agape love is a sacrificial choice of the will, not an uncontrollable feeling or a natural response. Because of our fallen human nature and inherent selfishness, attempting to manufacture affection in our own strength simply results in spiritual hypocrisy. Genuine Christian love means relying completely on the Holy Spirit to bear fruit through us, reflecting the exact same grace God demonstrated when Christ sacrificed Himself for us while we were still unlovable.

Source: www.gotquestions.org/loving-others.html