Spanish language Q&A Forum

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.

My understanding was that the accent falls on the penultimate syllable unless another syllable is accented. Given that where does the accent fall on “peinar”?  Is it not split into pe in ar?