Everyone knows the story of St. Martin and the beggar. (I'm pretty sure a picture of St. Martin cutting his cloak in half was in one of my "Saints for Boys" booklets when I was a lad. Cool, because there was a sword and armor, but nothing like St. Sebastian's arrows.)
First, there's the reaction of St. Martin on seeing the beggar:
... Martin met a naked pauper in the gate of the city of Amiens, whom all would pass by, although the wretch begged them to take pity on him. Martin, who was full of God, understood that, since others showed no pity, the pauper was reserved for him.
What a wonderful understanding! That others showed no pity didn't cause St. Martin to criticize them, either openly or within his heart. Being "full of God," he took the pitilessness of others as proof of where he was to direct his own pity.
This happened before he was baptized; St. Martin was in no position to preach to, much less scold, those around him. Instead, he simply did what he could.
But notice the reaction of the onlookers on seeing him cut his cloak in half:
Meanwhile, some of those standing around laughed because, having cut up his clothing, he seemed disfigured. However, some who had a more sane mind, groaned because they had not done something similar, especially because they had more and could clothe the pauper without making themselves naked.
In simply doing what he could to help the pauper, he preached the Gospel to those standing around. The lesson, as ever, was received according to the mode of the receiver.
Sulpicius Severus's comment that the ones who groaned "had a more sane mind" pairs well with this post at More Light:
One of the side effects of striving for holiness is remaining sane in an increasingly insane world. OK, maybe we will never attain holiness, but I am sure that the sheer effort to get there is enough to keep one sane.
So what do we have?
If you see a need no one is filling, fill it.
If you see a need you can fill but don't, you're in trouble.
If you can't see a need right in front of you, you're nuts.