I realized that because I was earning well each month, I was indulging in more without really noticing it.
So, when you're budgeting, always look at both sides: how much you spend and how much you earn. The latter figure has a much greater impact than most people realize.
I think it's a pretty basic thing to understand for any individual who is earning and managing their finances themselves, because our lifestyle changes based on how much money we earn, and you can't really stop that from happening, changes happen automatically. When you are earning less, you will know you can't afford much, so your mind will automatically make you adjust with normal stuff, but that changes as soon as you start making more money, now your mind knows that you can afford better things, so you start spending more on the same things that used to take less money earlier when you weren't earning much.
This thing isn't limited just to materialistic things, it happens with food and everything else that you do. We all have desires related to every single thing in life, be it our house where we live, the food we eat, the cloths we wear, and the places we go to, and these desires need financing, which is why when we start making more money, we start fulfilling our desires and wishes. If we used to eat whatever we could get in the budget before, we now start eating things that we like eating because we can afford to do that.
This is basically how your expenses adjust based on how much money you earn.