Sadness is the signal that you have lost something that mattered.
I want you to notice how much information is packed into that sentence, because it changes how sadness gets read. Sadness never fires about something you didn't care about. That is mathematically impossible. If you feel sadness, then whatever is being grieved, a person, a relationship, a version of yourself, a future you'd imagined, an era of your life, a version of your body, a friendship that faded, a role you no longer play, mattered.
Which means sadness is, in a strange way, the most loving emotion you have. It is evidence of what you love. It is the reading that tells you what was worth having.
Sadness has range, like the others. Wistfulness is sadness reading low. Grief is sadness reading high. Both are the same instrument measuring different magnitudes of loss. If you feel disproportionate sadness about something small, the small thing is usually standing in for something large: an accumulated grief, a loss you never fully mourned, a life you never got.
The mistake most of us were taught: sadness is weakness, self-pity, wallowing. It isn't. Suppressing sadness doesn't make you stronger. It just disconnects you from your own evidence of what you love, which over time makes it harder to know what to reach for, what to protect, what to grieve when it goes.
If you cannot feel sadness, you cannot feel the size of what mattered. Numbness isn't strength. Numbness is a broken instrument.