As you've already stated, it shouldn't be an intellectual achievement... though it certainly can feel like one. The impact of the revelation probaby depends on how heavily indoctrinated you were.
My parents were extremely religious (Catholic) people while I was in grade school. On an instinctual level, it never made sense to me. At best, I could conceive of a collective unconscious. However, there was something very comforting about prayer and ritual that I wanted to hold onto. In highschool I began to realize the tradeoff. I could feel guilted, gullible, and confused 99% of the time, and then buy into faith's illusory promise in moments of dispair. Choosing truth and freedom over faith was extremely empowering.
Funny that you used your children's acheivements as a metaphor. Today I overheard a collegue complain that her child's pre-school was having a 'graduation ceremony'. She said that when she was growing up in India she didn't celebrate until she was finished with college.
I wonder if milestones help or hinder. Do they motivate you to keep going? Or do they cause you to believe you've reached the end?