Me love cookie

Sounds like you want to set a budget and then make sure you’re adhering to it. There are a few options for that. YNAB (you need a budget) is popular in the commercial space and actual budget (https://actualbudget.org/) is an open source project that’s similar. Firefly iii (https://www.firefly-iii.org/) is another open source budgeting software. Those are all web-based.

I’d expect a spreadsheet could be ‘good enough’ depending on how much integration and automation you want.

Do your best. Make the best choice you can and consciously decide against second-guessing yourself later. Feel free to learn about yourself from any inclination to second-guess, it could be your morals chaffing against your actions.

Be kind. To those you love and those you don’t. Give yourself some grace when imperfections monopolize your focus.

Learn about yourself. It’s going to be a lot easier to make decisions when you know yourself.