Truth is the expression of reality. It is often easy to know the truth when it hurts. If an idea doesn't work, it is because it doesn't reflect reality. It might be impossible to understand reality with our limited senses, but we must try our best. It is like a mathematical problem where we forever approach the limit without ever reaching it. I guess that some people are just better at accepting good enough instead of perfection.
Yes, truth is important. It is important because reality must be contended with and there is no avoidance. Whether the truth is bitter or sweet makes no difference. To any effect, the world is indifferent. In a world of cause and consequence, things must be as they are.