If you don’t deal with your doubts, you will be given over to a spirit of grumbling. You will live that way and die that way because your doubts cannot simply be suppressed. They must be pulled up by the roots!
Just three days after Israel’s deliverance from Egypt, they encountered a new test. They had been singing, shaking their tambourines and testifying to the power and strength of a mighty God. They were boasting that He was leading and protecting them — and then they arrived at Marah, which means “waters of bitterness.”
This was an example of how God just keeps allowing us to encounter crisis after crisis until we finally get the lesson He is trying to teach us. If we keep refusing to learn it, a time comes when He gives us over to our own bitterness. “And they went three days in the wilderness, and found no water. . . . And the people murmured against Moses, saying, What shall we drink?” (Exodus 15:22, 24).
On Sunday they were having a great time — singing, dancing, praising! But by Wednesday they were in trouble; another crisis, and they were falling apart. How could they lose their confidence so quickly? Because they had never had any! They had never had that foundation truly built under them. 
So again they failed the test. They had learned absolutely nothing from their previous crises and again they missed an opportunity to shine forth the greatness of their God. They even began to take His goodness for granted. They had no food, so He sent them manna from heaven. He dropped quails out of the sky, piling them up outside the camp three feet high. But not a word of thanksgiving was heard. Instead, the people turned to greed and hoarded up all that God gave them. And then Israel became stiff-necked!
What a shame it is to go from crisis to crisis and learn nothing in the process. It carries with it a curse and you will be given over to a spirit of murmuring.