Once there was a switch-man who used to operate the controls of a bridge for ships and trains to pass by sitting in a small booth on one side of river. During most of day bridge was running up and down to make way for ships to pass through freely. But at certain time, a train would pass through for which the bridge would be turned sideways across the river, allowing the train to cross. One evening when switch-man was waiting for last train to come, he stepped on to the controls to lock the bridge sideways for train but he found that locks controls were not working. He knew if bridge was not locked properly then it would wobble causing train to jump the tracks and go crashing into the river. Switch-man left his booth and hurried to other side of bridge so that he can manually lock the bridge in place. To manually lock bridge he would have to hold the lever tightly as the train crossed. As switch-man heard the sound of train coming, he hold the lever tightly to keep bridge locked as he know many lives depends on his strength. Suddenly he heard a sound from the other side of bridge, "Daddy where are you?" He saw that his 4yrs old son was crossing the bridge to look for him. He almost left the lever to run and snatch up his son and carry him to safety.    but he realized that he could not get back to the lever in time for the train to pass safely.   either the people on the train or his little son would have to die.    it took a moment to make his decision. Train passed by safely on the bridge and no one on board was aware of the fact that a little kid was thrown into the river by on rushing train. Switch-man was sobbing, still clinging tightly to lever even after the train has passed. Neither did they see him walking home more slowly than he had ever walked before, to tell his wife how they had lost their son. 
We can never imagine the pain a person has to go through because of sacrifice he make. We must appreciate and be thankful to those who silently sacrifice and endure pain for sake of others. 