Generally Truthfulness is understood merely to mean that we must speak the Truth. But we the word Truth in a much wider sense. There should be truth in thought, truth in speech, and truth in action. To the man who has realized this truth in its fullness, nothing else remains to be known , because all knowledge is necessary included in it. What is not included in it is not truth, and so not true knowledge; and there can be no inward peace without true knowledge.
If we once learn how to apply this never failing test of Truth, we will at once able to find out what is worth doing, what is worth seeing, what is worth reading.
Where there is Truth, there is also is knowledge which is true. Where there is no Truth, there can be no true knowledge. And where there is true knowledge, there is always bliss and peace. There sorrow has no place. Truth is eternal and so is the bliss derived from it.
Devotion to this Truth is the sole justification for our existence. All our activities should be centered in Truth. Truth should be the very breath of our life.