Yea, I've been trying to figure out of it's a incoming or outgoing problem. And I'm not sure. And this is where I might need help. Here's a small breakdown of this past month's bills.
Income: $5,600;
All Bills: $4,637;
Gas-Tolls: $300;
Groceries: $700;
That put us $37 in the hole without anything else coming out. So no tithing, no extra spending of any kind. Very tough with those numbers. So I think it's a spending problem as we just have too many bills.
Lots of good advice in other posts, and I don't want to pile on. But maybe can offer some help on the "Mentality" approach you mentioned.
I was in an not too dissimilar situation a few years ago. Car Loan payments, student loan payments, etc. and throwing 'generic' budgets together. My wife and I would put together our budget based on what we were already spending and what we wanted to do. "Groceries have been costing us this much, so this is the grocery budget." etc. Basically a "Top-Down Budget", which didn't really help the situation. After paying my bills, here is how much is left, and then just magically spending all that on groceries and things. Mainly because it was available. I wasn't focused enough on it.
You mention a mentality shift, and that is what we needed as well. The quote I remember hearing that flipped a switch for me was "You either tell your money where to go, or you just end up wondering where it went." We spent several years just wondering where it went... And now that I see where it was going, after the fact, I am mad at myself for wasting so much money for so long.
Instead of listing out the things we wanted and then going "here is what our groceries cost" approach, we shifted to "this is how much we have to spend on groceries", what meals can we get put together for less than this amount. We got it pretty low when it was just the two of us. We would get a pound and a half of beef, and cut it into 4ths (8oz) rather than previously making a full pound each meal and throwing away the rest. I ate PB&J everyday for lunch for weeks on end. We went probably 18 months without going out to eat at a restaurant, and only a handful of fast-food visits. Our friends understood, most anyway, a couple of them we just don't talk to much anymore. We made our "Menu" ahead of time, and only bought the groceries we needed for those meals, no snacks or extras. The last week of every month was a "here is what is left in the fridge and pantry, what meals can we cobble together with this items (so we don't throw them away) with buying as few items as possible." We would sometimes end up with a weekly grocery bill of $20 for that week, I do recall one time we had to buy an onion to finish off the week and that was it. That is that "Gazelle intensity" they talk about - you have to get serious and hyper focused. We viewed our debt as destroying the life we wanted to live.
We now drive a 10 year old paid-for vehicle, and recently purchased a 3 year old vehicle we paid cash for. Some of our friends are blown away that we paid cash for a used car ($28k Ford Edge SUV, not a $60k used Lexus). We still have a 'car payment' now, but we pay ourselves, it goes into an account and earns interest. And every 5-6 years we replace one of our vehicles with the cash in that account. "Oh, so you still have a car payment. It's not that different..." they tell me. Oh, but it is. If something bad happens one month, I can choose not to pay it and nobody is going to come after me. Also, it is currently EARNING 3.2% interest, rather than me PAYING 8.7% interest. It really is changing the way you think about your money and what you want it to do.
If you have been doing a top-down budget, I would strongly recommend doing a bottom-up budget. I bet there are some areas you could squeeze a little tighter. You aren't bringing in that much less than me, but your bills are noticeably more than ours are, and we have a kid in daycare.
We run a $0 budget. (I am not sure if that is the official name, but that is what we have been calling it). Every month we end up with the same balance in our checking account at the end of the month, and have 12 savings account 'envelopes', most of which are sinking funds. We never have "Extra Money" at the end of the month, because it is always given an assignment. We tell that money where to go, and what we want it to do. Every dollar has a job.
That quote - "You either tell your money where to go, or you wonder where it went" - was the game changer for me and shift in my mentality. It is all possible, but you've got to completely change how you think about money and ignore all the outside noise.
Like you I also hated telling my wife no, but we both had to be in it together to get it done. We both needed reminders from each other of what the goal was, and that the 'pay off' was worth it. Now we have quarterly "Budget Meetings" and if there is something she wants, we look at the budget together and see where we can fit it in. So it becomes a lot easier to say yes now.