Food!
My family of three (well, 2.5... We have a toddler) regularly goes over our $400 monthly budget. We even pass $500 sometimes. Facepalm.
I don't cook. I can, but I am terrible at it and I need a good recipe and every ingredient it calls for (very expensive, usually!). So my husband does the cooking. He is good at throwing together whatever is in the house, but he doesn't really think about the cost of ingredients. We used to be vegetarian years ago, but it was before we started budgeting so I don't know if it made a big difference.
We also buy food pouches for our toddler (gasp! I know.) they are just so much healthier than what I would otherwise have on hand for her. I always try to get them on sale but even then they're expensive. We probably blow $30-$40/mo on those.
Our worst offense is Starbucks. I know that's a terrible confession on MMM, but no matter where we live there's always one nearby, and it's just a nice reason to get out of the house for a little bit. We have another baby on the way and i don't see that habit going anywhere. Especially when it's bad weather, just having that destination as a reason to get shit together and get out is really nice. It makes you feel like a person again if you haven't otherwise been able to do anything other than take care of kids and maybe feed yourself that day.
Plans to improve? Always. I'm hoping we can substitute a trip to the playground for the Starbucks runs now that the weather is better. We go though about 1 food pouch per day, which we could possibly cut down if I can get my little one to eat whole fruits and veg with less resistance. A long-term goal!
Going to costco LESS often I think will help a lot too. We get our meat there, and always spend too much no matter how restrained we are. When we haven't gone for a while and we don't have meat, we tend to have vegetarian meals which are generally cheaper. Plus our kid likes beans way more than meat!
I'm also hoping my impulse spending goes down once I'm past the morning sickness part of pregnancy, but.p it will probably just switch to cravings instead! :)