And after buying that expensive thing, now what? are you really happy? of course you are, you somehow feel relieved but after a few weeks do you think you're still happy? maybe you are but your happiness has diminished for sure.
It just shows that no car, house, jewelry or shoes can give you forever happiness because after buying those things... you will come back to your default state again. And if your default state is always being jealous of others or trying to prove others that is why you are buying those things... then you're in big trouble my friend.
Keep in mind that having new things will only make you popular in one day, people will admire you and praise you but after one day of being popular... they already forgotten that you buy those things, they will never treat you special anymore because you don't have anything new to show.
And if you're not that rich who can always afford to buy new things without getting poor then you have a big problem. You will be swallowed by a quick sand and it will be very hard for you to escape it. You will become broke, you will be trapped in huge debts and that shit will make your life like hell.
It is better to keep your money than to spend it for useless things. Saving money is the number one step to being rich. If you are saving money rather than spending it then you will feel rich because your financial status is growing, you will feel secured, you will feel that your life is progressing in some ways.
Because all the spending does is make you an addict to spending, the worst thing is you are buying stupid stuffs that will not even make your life better.
Spending your money for stupid stuffs will only give you a few seconds of happiness, I am very sure there are lot of times when you feel regretful after buying something because you realized that those things are useless.