Mark 12:31 NKJV
And the second, like it, is this: ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these.”
If you don't already know, the verses just before this one is where Jesus tells His disciples that the greatest commandment is to love the Lord your God with all your heart, all your soul, and all your mind. And then he tells them (& us) that the second is this; to love your neighbor as yourself. It doesn't say to love them only if they are good, nice, kind, or even if they love you back. He simply says to love them. The lack of conditions in this verse obviously means for our love to be UN-conditional. Unconditional love; which, thankfully, is the way the Lord loves us.
Granted, there are people in this world who are hard to love. I'm sure I, myself have fallen into this category from time to time. But Jesus says to love them (& us) just the same. He even goes several steps farther by telling us in Matthew 5:44 to love our enemies, bless those who curse us, do good to this who hate us, and pray for those who persecute us. I'm pretty sure that people who fit the description as our hateful, cursing, persecuting enemies, are not going to cause a loving "feeling" to bubble up out of us. This is where the fact that love is often a choice comes in. You may have to consciously make an effort to love these people, at first.
Think about it from God's perspective as best as you can as a finite being. Do you think it would be easy for Him, if He went by His feelings and His perfect, sinless, almightiness, to love the sinful, shameful, disobedient creatures that we are? Consider the Israelites. God sent Moses to free them from bondage, to rescue them from the pharoe's cruelty, and deliver them to their promised land! Were they grateful or even obedient? No! They complained incessantly. They fought and bickered amongst themselves. They even created graven images; idols, that they had the nerve to call their God! Offering it sacrifices of praise and worship that is only due to the true and mighty God, Yahweh! The Israelites couldn't have been easy to love if God went by his feelings alone. Their actions weren't the kind that would cause one to feel in a loving way toward them. But, God loves them still. They are His chosen ones; His beloved. He made a choice and no matter how sinful and wretched they behaved He loves them unconditionally.
He was showing them and us how to love. He was leading us by example. He was showing us then and is showing us even now, how we are meant to love each other.
When we make a choice to love ALL people regardless of their actions or worthiness, it will become a habit. Eventually the choice to love becomes less of conscious decision and more of a natural reaction; a part of our nature. Imagine if more of us operated in a loving nature; in the nature of God. How different the world would be!