You can get only what others give you willingly, and you can spend only what you have.
The keyword here is will. No one can force you to do anything. You do anything in a capitalist world solely for your own reasons, not for the demands of others, while keeping in mind that, if what you do is not productive, you won’t get anything out of it, and you cannot force others to sacrifice their time, energy or money for you, for free. The system emphasises a central fact: There is no free food. Someone always pays for it. In a capitalist system, you pay for your own food. There is no way for you to force anyone to feed you.
Ruling principle of the capitalist system is Justice. The market will judge your worth and compensates for your services accordingly. If a stupid employer won’t pay you enough for your worth, the intelligent one will hire you. Better judgement wins. If a stupid employer pays you more than your worth, he’ll waste his wealth, and loses his market share in the competition against his betters, who hired better people for the same cost. Again, better judgement wins.
To understand capitalism by contrast, take a look at the current alternate forms of statism, where the Government forces you to act for reasons which are not your own, forces you to pay for services that you do not want to use or endorse, forces you to hire incompetent people on the basis of their need and not their value to your purpose, forces you to discriminate on the basis of gender or economic status, and constantly infringes upon your right to act on the judgement of your own mind, which is a corollary of your right to your own life.
– Avinash Kumar, 19 July 2020.
Note: This article is originally my answer on Quora to the question: Can you explain capitalism in a single line?