Are nostalgic views homogeneous?

I've heard the song Ojos Triste, it was very popular when I was little, to tell the truth the Spanish version is one of my favorites but currently Selena and the Marías released a new version.

It's beautiful, I feel like it gives it a fresher touch since unlike when Jeanette sings it, she feels sad, do you understand? 

I was wondering if sad looks have a standard for being categorized as sad, admirable, or cute. You know what I mean? When can crying be considered cute? Why is it popular? This question arises from a sense of nostalgia. I believe there are looks that don't express sadness when crying. It will sound as if I'm invalidating the feeling.

It's not like that. I kind of wonder when and why it's considered a rule to be cute enough to cry. Isn't it enough to feel the other person's gaze? I've seen few people cry in front of me.

They all make you feel something, no matter what it is: anger, sadness, nostalgia, happiness, laughter, or satisfaction—there is something, and my questioning starts from there.

Is there a rule for expressing sadness through crying? For conveying with your eyes what you can't express with words? 

It's a silly thing I thought, the song reminded me of the looks that express.