Read it again people. Read it every year. Then go read the Constitution. Do we live up to these ideals all the time as a country? Nope. Have we royally screwed up at times? Yup. Will we do so again? Yup. Does that invalidate these ideas? Not at all. This is a goal, a target. As the old saying goes, "If you aim at nothing you will hit it every time." So aim at something lofty and work to be better.
IN CONGRESS, July 4, 1776.
The unanimous Declaration of the thirteen united States of America,
When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
We hold these truths to be self-evident, that all men are created equal, ...