If I speak in the tongues of men and of angels, but have not love, I am only a resounding gong or a clanging cymbal.
Remember this, when you write. You need to love your characters. No matter what you put them through, if you don't love them, nobody else will care what happens to them. Nobody really cared when a red shirt got killed on Star Trek. They weren't written with love. They were just disposable elements. When Spock died? Whole 'nuther story. And if the red shirts had been loved by the writers? Then, yes, that too would have been a whole 'nuther story. Something more akin to this century's Battlestar Galactica.
Loving your character shouldn't blind you to her/his flaws. If it does, you have just stripped away dimension, leaving your character flat and lifeless. It should instead give you more insight into the character's psyche, a better understanding of those flaws, and the ability to sympathize with them. Love them, not despite their flaws, but as a whole package, flaws and all. Just like in real life, the flaws are inseparable from the rest of the person, and it is often because of the flaws that people can be truly good and amazing, and most important of all, interesting.
Lest you think I speak only of our heroes, our beloved protagonists who must save the day from evil and deliver us from bad coffee - I do not.
It is perhaps even more important to love our villains than it is to love our heroes. Sympathy for the devil? Yes. Absolutely needed. Your villain needs to have reasons to do what s/he does, and it needs to seem like a good reason to the villain. And that means that you need to understand your villains, you need to be able to find the headspace where what they do makes sense, even if it doesn't make sense in any objective way.
As writers, we want our readers to find our villains believable. We want the reader to care what happens to them. We want to invoke strong feelings from the readers about our villains. And we can't do that if we don't love them enough to get to know them.
That concludes today's reading. Let us pray.