Mental Accounting is one of the causes of our biased decision making. We distil complexity into jars. Stories and categories we understand. Building up connections through chunky words, sentences, paragraphs and concepts we grasp and buy into. Money can be used for anything. It is “fungible”. Ideally, we would be able to see that everything is connected, and the specific jar you use does not matter.
In reality, we need to create rules that help us get to our destination. This might mean having multiple bank accounts for different purposes. Having savings deducted automatically so that you don’t see them, forget about them, and don’t even consider firing (spending) them. Specific accounts for holidays. It might mean having individual accounts, and common pools, to separate or pool decision-making as necessary. Mental Accounting can be used in positive and negative ways.
The Endowment Effect is how we value things we already own more. So if you are offered $5 or a mug, you might take the $5. But if you are given a mug, then offered $5 for the mug... you might refuse. The mug is yours. That is a story. Reflecting on the very human way you make decisions is important to make sure they connect and add up in a way that is consistent with your long-term values.