I have had this problem for a while, and no Spanish speaker can readily explain it:
In English, an adjectival form can only describe a noun; for a verb, you must use the adjectival form. The only exception of which I know is "I am well." Because so few English speakers have good grammar these days, "I am good" has become a colloquialism that is acceptable. But one can never say "I cook good" or "He lives happy".
But in Spanish, I see this all the time though Spanish speakers also acknowledge the rule that adverbs, not adjectives, describe verbs. In this lesson, I just saw it again:
Espero que vivas feliz en tu apartamento nuevo.I hope you live happily in your new flat.
Any clarification of this usage would be gratefully accepted.