Much of the history of Western philosophy has concerned itself with questions similar to those of Western religion. Ultimate questions about where we came from, what our purpose is, what the ultimate structure of reality is, and what happens to us after we die. Questions of this sort belong to a branch of philosophy called metaphysics because there is no possible physical way to find their answers (these topics are meta or beyond physical). There's no physical way to know what happens when we die, just as no physical evidence can tell us what the ultimate purpose of life is, or whether our wills are free or wholly determined. Since experience can never lead us to definitively answering questions like these, all of our theories about metaphysical issues are, by default, speculative.
But lack of the possibility of evidence has not made those questions burn any less fierce in our psyches. Since lived experience doesn't readily supply us with the answers we seek, history is full of stories about how the divine came into physical form to impart such unknowable knowledge to us. But for some of us who are inclined to view those stories as fables, we think that our mental resources should be focused on problems that are at least potentially answerable through an appeal to evidence.
If we resist this temptation to speculative metaphysics then our values must lose the status of Divine, Natural, or Universal; to be shown for what they really are: radically contingent. Radically contingent in the sense that our values are not emanations of a divine, natural order; but rather the result of everything in the past that has led us to them. How we were raised, who we have spoken with, what we have read, who we have loved, where we have traveled -- these are the true sources of our beliefs and values -- even when we're tempted to think that their authority comes from something bigger than our own lives.
Coming to terms with the contingency of your values means reminding yourself that you had no say in where or when you were born, and that if one small moment in history had been different, things could have been wholly otherwise for you. Such an acknowledgement doesn't necessarily destabilize the values that shape our lives, but it does humble them. It's an acknowledgment that while they may work for us, they are not universal, timeless or otherwise absolute. Understanding the contingency of your values and opinions is an anecdote to the xenophobia that drives so much injustice and exclusion because it invites us to entertain the possibility that future experiences might alter our current beliefs. Some of the most intolerant zealots are those unaware of the contingency of their values -- who think that their values reflect the natural order of things (and the idea of "natural order" depends highly on metaphysical speculation). They do not.
Perhaps ironically, however, you may still choose to fight and die for your values even after acknowledging their contingency. You just have a better understanding that you're fighting for yourself and your community and not for God or Nature.