What am I?

An Introspection:

I can perceive on another level,

yet I've never seen anything at all.

On my existence, all men revel,

before they walk upon madness and fall.

I can make men wise and thoughtful,

but I can also shroud them in envy.

I can give men goals, and make them soughtful,

but I can also make them never see.

Before you judge and accuse me inept,

you must realize that you have been deceived.

Into the depths of your soul, I have crept,

and all the pain has never been relieved.

If we all have one until we must die,

then I ask this one question, what am I?