I have read some parts of 'The Varieties of Religious Experience: A Study in Human Nature' by William James.
I experienced some mystical graces since when I was a young girl.
I remember sitting in my home alone and some man's voice told me that I was never alone but He was always with me.  I looked around and there was no one but me.   That happened a few times.  Some times I get this insistence without hearing the voice.  
My mother did not practice any organized religion.   I became a Catholic, when I married a Catholic husband.  Our parish an adult formation minister lead me to an imagery prayer and Lord showed me how He was sitting on a big rock and watched me, a toddler, playing with dirt in the middle of farmers field.  That was what my mother told me how I played with dirt, wonder off, and got lost during the Korean war time escaped to country & was no baby sitter available.

I read some retired Catholics still not sure about the existence of God and I do not know what to say.