I haven't read any of the responses yet, but my most Antimustachian act was marrying my soon to be ex husband.
I wasn't good with money through out college, but once I graduated, I started gaining some ground. Started paying off $10K of credit card debt I wreck up while in college. Set my student loans on auto pay at 2.5 times my monthly payment. Had a small savings accounts. Started an Roth IRA account.
Few years later I met my husband. It's been 16 years and I truly feel that there hasn't been a single smart financial decision made between two of us in that entire time. Every so often I would "wake up" and get angry and pay off credit cards and try to get some savings going, but it wouldn't last long with him pulling the other way and me getting tired of fighting the losing battle. So usually, once I paid off all credit cards and we were back to zero, I'd give up and it would start a low slide backwards.
In August 2013, we had $163 (that's dollars, no zeros there) in the bank, $6K on credit cards, and were planning a $3K vacation. I got so mad (mostly at myself) and after we came back from that vacation (I know, you don't have to say it) I set out to pay off all credit cards.
By January 2014 we had $3K in the bank account and zero credit card debt.
At that point it was clear that we are going to divorce. But with zero financial cushion it wasn't possible.
To fix this, I had to basically go through the process of losing every last shred of respect for him. I opened a separate bank account in my name only and started stashing there every penny I could get my hands on. I put him on allowance and questioned every single transaction that came through our joint bank account. I took away his credit cards and was monitoring his credit history and all his credit card online statements religiously. It got to the point where I was checking bank account and about 7 credit cards multiple times per day and txting him and questioning about every $6 charge from 7-Eleven as soon as they appeared. It was maddening, but I was a woman on a mission. I wanted a divorce and I was going to have at least couple pennies to rub together when that happens.
I am all set to move out with my kids in July as soon as school ends in late June. We are going through divorce mediation and should have everything signed before I move out.
That bank account I opened in my name only right now has $50,000 in it (so $25,000 for each of us). There is another $7,000 in our joint bank account to cover mediation costs and kids' summer camp.
I would not recommend this to anybody. I have zero respect left for this man, who, even now while marveling at how much money we (I!!!) was able to save is talks about wanting to get a new MacBook while having perfectly working laptop.
And before anybody asks, yes he knew about the account and that we are getting divorced. I was very open and vocal about it.