How to create disk quota for single user / prevent hard drive from filling?

I have been searching for a tool to prevent the hard drive on my Mac Book Pro from filling up. There are lots of tool to free up disk space, but i am looking for an application, or a simple method, for "locking" 10% of the 250GB space I have on my computer. A system which forbids me to save new files on my computer when the amount of free space is below 10%.

The problem is that I am constantly hitting the limit of space on my hard drive, and as a result, when this happens, my computer is struggling to operate.

I have found this article, the second part about quotas could be a solution, but it is too complicated. I wouldn't dare to take a shot at it. http://www.cnet.com/news/how-to-limit-user-disk-space-with-partitions-and-quotas -in-os-x/

The article also talks about partitions, but I can't figure out if this will actually solve the problem. If let's say, disk space is partitioned into, for example, 220GB and 30GB, wouldn't my computer still be struggling when it hits the 220GB limit? Then i just have 30GB of useless space hanging around in a partition... or what? Another scenario would be something like having a partition only for "system stuff" and another partition for all "my files", but as you can hear i am not sure if this is based on a false idea of how a computer works and how I would actually implement it.

I find it weird that computers don't ship with a limit for how much of the hard drive space the user is allowed to take up. That the user actually is able to fill up their machine until the system starts failing.