Care your MFT
Why? Because MFT means all your data and your data is MFT.
When you create a partition on the disk, Windows reserves 12.5% of the total disk size for MFT structure. It is located in the beggining of the disk. Such a location improoves performance itself and that is more important it doees not fragments Master File Table.
To avoid dramatic performance issues, we recomend you never drain free space lower then 12,5%. Let's see what happens if you void this recomendation.
When free disk space is lower then 12.5% Windows reduces MFT reserve and allows user to write more on the disk. But you are writing what? A file! So it should be described in MFT. So you fill up the MFT too. After the space is gone, user realises he (or she) should delete something to be able to write something. User removes data here and there and get's some free space. Yes, but Windows reserves part of this free space for MFT too. So the main part of the MFT is located in the beginning of the disk and the rest is spreaded on the whole partition like a jam on the butter.
Also plesae do not forget, there is two copyes of MFT, and both of them should be updated MANY times during a simple imput/output operation!
We can reccomend you some cure for this disease. You can format your disk often, and everytime have a headache have you backed up everything or lost your data, not a good advice. You can get yourself a good disk defragmenter software, that is able to defragment MFT. Suitable for rich people that want to cure consequence not a reason. Or you can watch your disk space by yourself and never overfill your disk more then 100%-12.5%=87.5%. There is also another feature for the last method. Formatting your disk in some cases can overwrite your deleted files, and it will be impossible to restore. Defragmenter makes same effect, but it has even more chances. So whatch the your disk space level it is the best advice you can get.