There was a time when I realised that I could not tell the difference between praying and merely talking to myself. I realised that the world looked and worked exactly the same even if there was no one listening. Of course, I still looked for answers and convinced myself that events in my life were "providence".
Then I realised that I was the one choosing which events were "answers from God". I was the one choosing what God was apparently telling me through scripture. I was doing the whole thing. I couldn't tell the difference between God really working in my life, and me just selectively interpreting events and messages as "God working in my life". Perhaps there was no difference.
If I was the one who ultimately decided which bits were "God speaking to me" and if I was the one who ultimately interpreted "what God was trying to tell me", then how could I know I wasn't just fooling myself?
The answer: I couldn't.
Every time I prayed after that, I couldn't shake the feeling that I was just talking to myself. Over time, I came to see that that was very likely all that was going on. Then I began to see that all of the things in the world that I had previously attributed to God made just as much sense (sometimes even more sense) without a god. The attribution was again just me making assumptions about the world.
People told me, "That's why you need faith", and they quoted Heb 11:6 to me.
But then I wondered, "What is faith and why is it so important?". If there was no evidence, and if there was no way to know, then how was this faith distinguishable from self-deception?
It wasn't long before I discovered the answer.