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The challenge is to spend only on essentials for 21 days. That is, during that time you should absolutely avoid all unnecessary expenses.
It is advisable to do it after you have spent a lot or when you need to collect money in a short time.
Practice it for a short time: doing it for more than three weeks can be very exhausting.
Avoid all unnecessary expenses: this method is based on spending on what is strictly necessary to survive, for example, housing, food and transportation, no more.
Record your expenses: during those three weeks keep track of expenses and savings, so it will be easier to create good financial habits.
Pay in cash: the creator of the method explains that buying in cash generates awareness about our expenses.