I have had this many quoted to me before and was told, "See, your biggest problem is that you just don't have enough faith in god."
The worst part was that I believed it and spent hours praying and days of fasting so that god would increase my faith. The bible promises that if you ask that, god will answer your prayer. The fact that it never happened for me, that i never felt that inner peace that so many Christians say they get from god, was pushed me over the edge into disbelief.
When you are reading the bible, praying and fasting and your faith decreases and doubt increases, you first start to blame yourself so you try harder. You pray harder, you start giving more of your money away. You loose 20lbs in two weeks due to fasting. Of course you do these things because you are desperate for relief and freedom from PTSD.
Then one day you realize you did everything god commanded of you, but he didn't follow through on his end. So you become angry with god. As the anger subsides it leads to...does he even exist? And when you finally decide:
There was no god that I failed to have enough faith in, nor was their a god to follow through on promise that you can now see were written by man; it is like a huge weight off off your shoulders. Realizing that your PTSD isn't due to lack of faith and that you are now in control of your own healing journey instead of waiting for some sky dude to follow through on his word, you gain an amazing sense of freedom and introspection on what role you play in your healing.