There is a universal custom of well-wishing and of blessing in the protocol of basic greetings.
Notice: "Good morning", "good afternoon", "good night", "good weekend", "have a good trip", "happy" this and "merry" that. There is an underlying reality in it all which is the fundamental need to be acknowledged and affirmed by the others. So much so that we regard it as an affront and as too utilitarian and inconsiderate to forego these niceties in our daily lives. It is a proof for the existence of God, because the question should be asked, why should it make any difference what others think or whether they are with or against. What do you mean by "good?" Answer: we are naturally oriented to relationship, and to unconditional love, i.e. good will. And there is One who is the very meaning of good, the One from heaven, God Himself, Jesus Christ.
Next time you feel slighted because someone neglected to wish you "good morning", etc., remember that all of the well wishing in the world has its source and real meaning only in the Lord. Remember that you feel bad because we need to bestow goodness on one another because we are the image and likeness of God Who is love. Our courteous well-wishing comes from Him and is directed to Him because...
We need to be like Him and to share his likeness with one another, the Good! That is why we must say and do "Good Day" in every way, for one another, for the further glory of God! our Purpose and Source.
The rule of kindness is part of what it means to say the "Jesus Christ is Lord!" Every tongue does indeed confess, even unwittingly, by well wishing. Philippians 2:11 Because Christ is the prototype of man!