No big moment, but a few smaller ones. In chronological order:
1. Dave Ramsey - realized how stupid debt is.
2. YNAB - found a budgeting system that worked better than the DR pen-on-paper speculation.
3. MMM - gave a purpose to frugality, a reason and motivation to do better.
Really, it was a series of eye-openers that gave me a completely different way to look at money, spending, debt, etc. I was raised by parents who barely made it paycheck-to-paycheck, always in debt, no savings, but still found money to go on vacation, eat out every week, have cable tv, etc. So I basically had to relearn how to handle money, because I had never been taught. Mr Tofu's parents are the same. No huge expenses - used cars, etc. - just daily small decisions that added up to a horrible financial life.
My parents are in their late 50's now and my mom mentioned to me over the summer that they don't always know where the rent money is coming from. She's told me about really stupid decisions they've made, in casual conversation, as if it's not stupid and this is just normal - because it is for them. It was smart, she says, to rent the bigger house for $2100/mo instead of the smaller one for $1850/mo, because with the smaller one, they'd have to put some furniture and my dad's boat in storage, and pay hundreds every month for that... and it was everything I could do to not say, "WHAT THE HELL IS WRONG WITH YOU? Get the smaller place and sell the other stuff; you don't need it!" I managed to bite my tongue, but I guess that was my AHA moment, because that conversation made me realize where I was going to end up if I didn't seriously buckle down. It also made me realize that I am absolutely not willing for that to be my future. They are going to be working forever, they will die with thousands of dollars in debt... no. No no no no no. I will cut back on anything and everything to avoid that. That conversation lit a fire under my ass, as well as opening my eyes to my own stupidity and how I was on track to be in the same place a few decades from now.
If you can't be a good example, be a horrible warning, right? I don't want to be the horrible warning for my kids.