Usually is an adverb of frequency and these types of adverbs can describe verbs and adjectives or even a noun phrase but they don’t modify other adverbs.

Adverbs of frequency may modify adjectives, in which case they come after the verb be. Is it because be is a linking verb (non a main verb), and the adverbs modify the predicative adjective(s) associated with it;?

I am usually late for the work. How do I explain this to someone who works hard? “But,

putting extra emphasis on be can change this a bit. The only time adverbs of frequency come before the verb be (when it is not used with an auxiliary verb) is when be is given extra emphasis in a sentence. I was

not fond of his writers. Or had an illegitimate interest in it. When

we read this, we can hear the stress being put on the word “.. is…? Though it comes before was, the adverb never is actually modifying the adjective fond.

Note that this construction can also be used when the adverb modifies be rather than an adjective, as in

“You occasionally are a nit-picker. But it’s good stuff.” If

we take the emphasis off be, however, the adverb would come after it as usual.