Truth is the accurate and complete representation of reality. We do not perceive reality. We only perceive a small fraction of all that is real - a representation of reality.
Truth helps us avoid two great errors in life: rejecting truth as error (Type 1 error) and accepting error as truth (Type 2 error). Both types of error can result in adverse consequences to ourselves and to those around us. We can improve the quality and length of our lives by reducing how often we make these errors and how badly we misperceive the truth.
We align our lives through trust. We trust that our perception is accurate enough and complete enough that we may align our lives with it and that we will not suffer adverse consequences
Our only other option is to trust a guide - and then trust that their perception is accurate and complete enough. We trust our perception of truth, or trust a guide. Jesus sent the Spirit of truth to guide us into all the truth. The Spirit of Truth is unlimited in his perception of all truth: physical - temporary and spiritual - eternal. He is completely trustworthy, faithful, and reliable. He knows the will of God and knows the will of God for us specifically. He knows the path God has for us, what our next step is, and when we are to take it.
We must make the choice of who we will trust to guide us into truth: ourselves or the Spirit of Truth.