Shri Nathji used to give the following illustration of firmness of faith:
There is a stake which has been driven into the ground. A goat is tied to the stake with a rope. As the goat pulls on the rope, the stake shakes. You hammer it further into the ground. A cow is tied to the stake and it pulls on the rope. The stake shakes again, so you hammer it in further. You test the firmness of the stake with a bull, and then with an elephant, hammering it in each time to make it firmer. Ultimately, the stake becomes so firm that nothing can shake it from its position–not even the stake itself!
This is the condition of faith. When tests come in life, the faith of man shakes. But he repents and makes a resolve to make it firmer. With the coming of each test, he drives his faith to a stronger and stronger depth, until finally nothing can shake it,–not even he himself!