Is it okay or normal to want to feel sad?

I'm an introvert, shy, quiet, and I recently have been heartbroken by my crush. However this feeling has always been around but it comes and goes. I like listening to slow or melancholy music which makes me feel better. My appetite has also recently delclined. I'm now starting to want to avoid my social circles which was something of the norm in the past, but now the desire of isolation is starting to come back.
Is it okay or normal to want to feel sad?
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