What is important is directly linked to survival.

In a 'dead or alive' situation, whatever is perceived as being
able to save one's life is considered important.
In this sense and reality, what is important can be either a truth or a lie.

All normal (not hypothetical) considerations of truth and importance of
various shades are reducible to the above principle.

Truth is impossible to know in the realm of abstract principles. This is because the means to know truth are limited by every person. If you think this is contrdictory than show/tell me your means to know this The fact of the matter is that truth is only known (can only be absolutely sure to be known) only to a being that has an absolute way to know something. A mind is far from this. When i say abstract realm i mean love, morals, fellings, things of this nature. They are subjective. If mean the truth regarding what reality is I think that , that hardly has any bearing on wat is important morally. Which is what I am assuming you are all talking about. But I think that importance is determined in a arbitrary way by everyone. (meaning no universal way to know for everyone, because every mind is different and the enviroment of that mind is as well I would have to know completely the status's of both to answer this completely. For each individual person.)