Truly noticing others is fundamental to their self-worth
Morrie Schwartz spent time working in a mental institution when he was younger. It was one of his first jobs, after he received his Ph.D. he would observe mental patients and monitor their treatments.
"One of the patients, a middle-aged woman, came out of her room every day and lay facedown on the tile floor, stayed there for hours, as doctors and nurses stepped around her. Morrie watched in horror. . . Every day she did the same thing: came out in the morning, lay on the floor, stayed there until evening, talking to no one, ignored by everyone. It saddened Morrie. He began to sit on the floor with her, even lay down alongside her, trying to draw her out of her misery. Eventually, he got her to sit up, and even return to her room. What she mostly wanted, he learned, was the same thing many people want—someone to notice she was there." (Pages 109-110)
We all need recognition. We need to feel that we matter. This doesn't mean that we should be running for glory and honor, but every human being has a basic and natural desire to be acknowledged as significant.
And we can give some of this significance to others simply by greeting them properly. We may not put much thought into how and when we say hello to someone, and we should ponder it more deeply.
The first thing to realize, which we certainly don't always think about, is that when we greet people with a 'good morning', we are actually giving them a blessing. We are telling them that we hope they will have a good morning. This is why, if you ever meet a grumpy person who responds to your 'good morning,' with a line such as, 'Who said it was good?', the response, besides being rude, is actually inaccurate. We are not defining the morning by saying 'good morning' rather, we are offering a blessing that it should be a good morning.

Regards
Avishal