Squandering is one of the things that Hawa commands and the mind prohibits. The best discipline regarding this is the discipline of Allah, all praises and glory be to Him, who says:
“But spend not wastefully (your wealth) in the manner of a spendthrift.” (Surah al-Isra 17:26)
Know that a person might be given the sustenance of one whole month in one day, but if they spend it wastefully, they will suffer for the rest of the month. If they are wise, and they spend it wisely, they will live happily for the rest of the month.
The cure of this disease of squandering lies in reflecting on the consequences of one’s actions and being cautious of the future possibility of poverty. This will ensure one restrains oneself from spending wastefully.