Regards,

There is no dichotomy between the true and man's knowledge; between existence and man's means of identifing that which exists. There is only one reality. Existence exists. Existence is identity*. A thing is what it is. Man's rational faculty is the faculty of identification. A rational non-contradictiory identification [valid concept] is knowledge of some thing; of existence.  You cannot have knowledge of nothing, or nothing inparticular i.e. without an identity.  Otherwise what would you be talking about? Nothing inparticular?   Using your means of identification, i.e. your reasoning  faculty,  you are able to arrive at knowledge by the method of logic, which is non-contradictory reasoning. When you use virture as the means for knowing reality [a mental action] and choosing physical actions according to the facts you identify, you are able to sustain your life.

Virtue is your means of establishing the relationship of your reasoning to reality.  Reality is absolute and your reason needs to know it.  It is up to you to identify and validate your conclusions using reality as the only standard for validation. If your thinking conflicts with reality it is time to correct your thinking.  Reality cannot be 'corrected' to fit your conclusions. It can be arrange or altered to suit your taste providing you follow its un-correctable nature i.e. a certain amount of heat will, when applied to a certain amount of water and tea, will at a certain altitude in a certain amount of time result in a certain event--- a cup of hot tea. It really is that simple.  
Rationality, Honesty, Independence, Integrity, Justice, Productivness and Pride.  This is how you function.  Right?
Best Premises, Robert Greer, Fairfax Virginia USA    *Ayn Rand's formulation:  See The Introduction to the Objectivist Epistemology by Ayn Rand. Also, on the subject of virture, you might enjoy the book titled:  Ayn Rand's Normative Ethics by Tara Smith [Cambridge Press]