It does not come naturally to me, and I had to learn to do it. Since it's not natural, it can actually distract me from whatever the topic of discussion is, in order that I pay attention to my eye contact with the other person or people with whom I'm talking. It's not easy, and often I wind up giving them a blank stare for too long, and they think I'm on drugs, etc. When the other person or people force their eye contact on me, it actually stops up my whole thinking process.
When I'm discussing something serious, I will excuse myself and explain my situation about eye contact (assuming the person or people don't already know me), and then I'll dismiss the eye contact thing while I make my case.
Charles