When you say sadness is just sadness, then you have gained freedom from sadness. It means being free from the obligation to label sadness as a loss of self-worth. If you let sadness go deeply into you, there is no way it is not going to touch joy.
It is great when you can laugh in your happiness. It is greater when you can laugh at your happiness. And it is greatest when you can laugh even at your sadness. You can then celebrate sadness. You can then celebrate all change.
The joy of laughing at your miseries is an unparalleled joy.