Can someone learn to love one's enemy and what does it really mean loving your enemy?

I was raised a Catholic and became agnostic at the age of 30 or so. I have heard teachings saying that you must love your enemy as you love yourself and those words always made me feel hopeful and sentimental, along with imagining how heroic it would be to be able to do such a great feat!

Personally, have you ever loved an enemy and how did you get to that point and what happened that made it possible for you? Are you waiting for a chance to prove you can do it or find it so unrealistic that you don’t care at all?