When you feel the "urge" to buy something, just wait a few days to analyse logically how much you WANT or NEED it. Because psychologically the urge can be an impulse. They will die down. Humans are more biased towards themselves with the status quo when their emotional state is not neutral enough.
The good or service you were hoping to buy may be sold out, or the
price of it may increase. However, the vice versa can also happen. The
economy is unpredictable.
You may forget about it if you don't write it down.