When you go from a corporate job to making your living as a writer, you also go from paychecks every other Friday to paydays that occur as infrequently as once or twice a year. (With luck, they are bigger checks than they were before.)
Here’s how it works:
First week after you get your check: “Let’s go out to dinner! Let’s go to Costco! And Trader Joes! And even Whole Foods!”
In the intervening weeks, you keep running the numbers. Will the money last? What will break (arm, toilet) that you didn’t budget for - and how will you pay for it? Will you get royalties? And if so, how much reserve against returns will there be?
Months later, the last week before you get your check: “Do you think that ravioli has been in the freezer for longer than five years? And if so, do you think it’s still edible?” “Sweetie, do you mind paying for your annual in dozens of quarters scavenged from the cars and the house?” “Wait - is that a Starbucks cup? How did you pay for that?”
What I've learned in the last four years: Money doesn't come that you expected. Expenses happen that you didn't plan for. And money that you didn't know you would get happens. And it all kind of washes out.