Financially accountable people buy what they can afford. And financially accountable people know what they can afford when they don't just have a budget, but also a cashflow plan.

As an entrepreneur, I run my household finances just I run my company's finances. Here is the how-to guide including an Excel cashflow template for your private household:

https://tomvogel.gumroad.com/l/how-to-stay-on-top-of-your-private-finances