I feel bad.
I feel (textures) badly.  (due to nerve damage in my fingertips)

I am good.
I do well.

I am bad.         [subject-pronoun   linking-verb   adjective]
I do badly.       [subject-pronoun    action-verb   adverb]

I look bad.
I see badly.

She is cheerful.
She works cheerfully.

They are happy; They feel happy.
They do things happily; They cook happily; They read happily. They feel the velvet fabric happily.