You currently own a smartphone.
It can do many things. Connect to the Internet. Take photos and videos. Do inner computations and run apps. Connect with other people. All in all it’s a great device, the pinnacle of humankind’s genius.
It also has its limitations. Unfortunately, it is not as powerful as the latest model that your friend has or will get in the near future. Or as the supercomputer of a big company. Its battery gets drained; you have to charge your phone regularly. It is also not indestructible. You need to take care of it, not throw it off a cliff, not put it in the fire or the microwave, etc.
But still, it is a pretty useful tool. And people generally treat it decently well. Although, sometimes, in a fit of anger, they may throw it on their bed, they usually don’t do anything too extreme because it’s an expensive item and so it is valuable.
Now, imagine that due to a lack of resources on Earth or some other reason, you cannot ever get another smartphone. You are stuck with this smartphone for the rest of your life. If the screen gets broken, you might be able to replace it, but if you throw it in the lava there is no coming back. Its battery will get weaker and weaker as you keep on recharging it day after day. And it will always have limited storage.
Wouldn’t you naturally find yourself taking much better care of it suddenly? You would try to charge it optimally in order to not wear down its battery uselessly. You would try to handle it with care so it doesn’t get broken. You would keep it clean so dust does not infiltrate it and mess up the electronics. You would be careful and selective about the apps you install and files you keep in the device as you don’t wanna accidentally install a virus that would render your device unusable. You would optimize your utilization of it in every way you can think of.
Once the news break out that, due to some resources limitations or some other reason, you will never ever be able to get another smartphone in your life, I’m sure these thoughts will come to you. And you will naturally be inclined to take the utmost care of your smartphone. This unique, unreplaceable and last smartphone has become your most prized possession due to its usefulness and rarity.
This “last smartphone” is...
...
You guessed it.
Your body.