I believe we are pragmatic creatures and if it works to call something "true", then we'll call it true. When that truth stops working for us, we'll stop calling it true. So, "truth" changes. It evolves. It comes and goes. We create it, control it, and use it. As far as one, absolute, undying, and unchanging truth that exists outside of ourselves, as we define it - well, we sure could come up with something, but are any of us really in a position to claim that absolute truth exists in the first place, let alone claim what that truth is?
One may say 1+1=2 is an absolute, undying truth, but the only reason this is considered “knowledge” is because we say it is so. We have constructed it mathematically and linguistically purposely to describe the world as we sense it. We created it out of experience and necessity for math, and we can destroy it if we want to.
My understanding is that we create and destroy truth/knowledge based on world experience and out of the desire to explain it for practical purposes (like to predict the weather, or simply satisfy our curiosity, for example) whether they be physical, mental, spiritual, or whatever. Questions like, "is X really true?" or, "does X really depict reality?" are only meaningful in so far as they are practically effective and possible to answer. It is pointless to question whether or not something is absolutely true (or to ask if I really exist, what a cloud really is, and other dumb questions), since we cannot know whether or not anything is absolutely true beyond what we have constructed to be true (such as 1+1=2), thus it is practically meaningless to think or talk about absolute truth at all. So I say we drop the idea and stay on this planet, working on practical truths (although speculating about impractical truths can be amusing).
To recap here - truth is made up out of practical necessity. We take the world and our experience of it, and we try to uncover the “truth”, but we don’t realize that we will always be the ones to decide what truth is in the first place, and in the long run, it really doesn’t matter, as long as it works. When we think a lot about questions like, “what is truth?”, we’re playing games with ourselves, and tricking ourselves into thinking truth is a thing that exists before us, when it’s just a description we made up in the first place for practical purposes (“if it is true that this is a rotting apple, I will not eat it”), but for whatever reason, people want to take it further than that. If you’re thinking of asking, “but how do you know?” regarding anything I’ve said here, then you don’t get it, because knowing involves truth and justification, and we just don’t have the means to objectively gauge either of those things, because they are subjectively manifested and dependent on us, the creators. The deciders. Truth is constructed and used in many different ways for many different purposes, and it is created and destroyed all of the time. This is where I decide to lay my blanket of truth, where you lay yours depends on your perspective, and whether or not it works for you. We cannot discover it - we can only create, allocate, and destroy it.