From a logical standpoint, it’s not that we are only sometimes ignorant, but we are always ignorant.
This is because in a state where a person is not ignorant at all, that person would know everything, because knowing everything is the only state where no ignorance exists whatsoever.
Therefore, we are always ignorant, simply because it’s impossible for us to know everything, no matter how we try. We can try to learn everything possible in the limited lifespan we have, but that will make us only less ignorant, not non-ignorant, because there are some things we may never know, and because of our limited lifespan.
A good example of ignorance is belief. Belief is always a product of ignorance, because belief is an attempt to be convinced about something you are not sure of, that exists. That’s what separates belief from knowledge - when you know something, you have no ignorance about the existence of it, because you know that it exists. Belief, on the other hand, is always based on an assumption that you think is likely to be true, not that is necessarily true beyond your thinking.
Hence why there are some things in our life which we may never be able to know for sure, and thus we either believe that they exist or that they aren’t, with the most popular example being the origin of existence. This is why the belief in one or more gods is a belief, and not something that even the most zealot believer knows for sure.
The only way to “combat” this inevitable ignorance is to optimally reduce it, but even if you are to be as less ignorant as you can, you will never be perfectly non-ignorant.
This is why I prefer optimality over perfection - perfection is likely to be realistically impossible, while optimality is always realistically possible, because optimality is always considerate of present circumstances and of the limitations of reality.
Due to the option of optimality, therefore, ignorance should be reduced even if it can never be reduced entirely. While we cannot be completely knowledgeable, we can be as less ignorant as realistically possible. As the cliché goes: "Knowledge is power" and indeed you may not know when your attained knowledge may help you in the future.