Originally Posted By: Faldage
I had forgotten the poem. He olvidado el poema.

"he olvidado" is "I have forgotten"; "habia olvidado" is what you want.

 Originally Posted By: Faldage
Un poco de sabiduría es(tá) una cosa peligrosa.

Here you want "es" as you are speaking about the characteristic of something. The verb "ser" (from which it comes), is used for personality and physical characteristics, as well as other things.

I poked around a bit, and stumbled onto this link: http://www.pierians.org I have no idea if there is any connection, but quite possibly there could be.