I'd been asked to recommend a student that demonstrated positive behavior. Immediately I thought of a child who makes a point to say hello.
It doesn't feel good to be ignored, especially in the workplace. I've been guilty of ignoring others. Attempting to justify it by suggesting I was too focused didn't make me feel any better. Of course, making a point to say good morning or the greeting of your choice does open up the possibility you'll be ignored.
It won't feel good, but you'll know the importance of hello.