If you have noticed that your CPU usage has been unusually high or that your fans have been constantly on, you may want to check your desktop. In previous years, it has been found that keeping large amounts, or even just a few large in size files on your desktop causes your computer to slow down. The main reason for this currently is because of Quick Look and the fact that it starts to load files in the current directory so that it can work even faster.

So, if your computer is running a little slower these days, check your desktop to see if you can remove all or most of those files.