There is no reason for the sun boast of its brightness, nor does an honest man about his integrity. If an honest man begins to boast about his integrity, then he obviously too proud and something is wrong. If he was integrant, there would be no need to tell everyone, because, that would be the same as saying, "Look, there is the sun in the sky!"
Using the sun as an example again, imagine if the sun went out. The world would be plunged into darkness! It is the same with an honest man. If the honest man were not there, the light that he was giving would be wiped out and there would be no more light to show the way of righteousness!
An honest man may very well warm your heart, and regenerate your strength to push on in the way of truth, just like the sun can warm you and dry you after a heavy rainstorm.
The sun also thaws out the land after a cold winter. The honest man can do the same thing on a sinner's heart, leading him onto the path to everlasting life.
So take example from the honest man. Try to lead the life of integrity and honesty. Your work may not be rewarded in this life, but it certainly will in the next.