Imagine you walk into the sauna and a person follows you in and starts to smile at you. Would you responded?
You said, "Of course! What if this person is my Miss Right / Mr. Right?"
Yes, that could be. But that could also possibly a subsequent heartbroken / grieving if that Miss Right / Mr. Right leaves you in a couple years. If you politely ignored, you could end up the day with a peaceful driving at home cuddling with your lovely pets.
This is Zhuangzi's Philosophy - Nothing is really good nor bad, it all depends on our view points. Zhuangzi focuses on the peaceful minds more than anything else - We have the chances of missing out a perfect love but also the chances of avoiding a torturing and suffocating love. You never know. And the only thing Zhuangzi wants us to bear in mind, is to protect our heart.
Zhuangzi said - Understanding is more important than love. Simply love without understanding is meaningless. Zhuangzi wants us to put our focus on ourselves instead of others - When we do so, we are keeping ourselves healthy and happy, and at that point, we do not need others to echo on the fact that we are good.
Zhuangzi did not mean to be cold or not engage social activities; he asked us to put ourselves first, and those people who really care, they would approach with a good understanding of you, that we do not have to respond to anyone's greetings just out of fear of missing out. Who knows how many "missing out" we are actually grateful for.