When I was 14 to 15, I tried to go to church (Catholic) with my Dad. I took classes; attended weekly (and then some) with him; read the Bible; etc..etc...
For me, it was
the errors, and the hypocrisy that made me eventually have to tell him that I didn't want to attend any more.
In particular, on the last day I attended, we all were singing (a feature of mass that I really enjoyed; along with all the shaking hands and saying, "Peace be with you."). The song we were singing was titled "By our love", for which the refrain is "They will know we are Christians by our love".
And all the time I was singing it,
I felt sick, since I knew (and still know) that Christianity is marked down in history for the Crusades; and The Inquisition; and for "Fire & Brimstone" fear mongering; and wars; and denying & turning back knowledge/truth; and for pain, hatred, and death.
I know that those nice people in the church with me weren't personally responsible for all of the undeniable horrors that Christianity has historically (and currently) been known for. And the priests in my Dad's church (where he was the usual 'reader/speaker') never used their pulpit to encourage hatred or fear..... But the smiling-faced, happy-happy-joy-joy was not syncing with my knowledge of the world and of the world's history.
I couldn't live the lie.