this basic idea of ynab comes down to: try to assign all your shekels to something, before you spend it not after the mental model is envelopes where you take all the money you and divy it up into envelopes and try to only spend what it's in each envelope at the end of each month, for each envelope you decide "do I want this envelope to have exactly X" or "do I want to always put in Y so that it keeps growing" so for example if you average 7K a month on groceries, you'd want to put in 7K each month. Some months you might spend 6K and some might be 8K but during the slow months you'll accrue a balance in that envelope such that in expensive months you'll have money saved to cover that in addition, you need to be forward thinking about what expenses are not recurring regularly and make envelopes for those as well

also, one of the fundamentals of ynab is to "roll with the punches" it's ok to take money from one envelope and give to another. You'll have to evaluate that based on your priorities