MBP running El Capitan freezes at login Since today, my mid 2011 15 in Macbook pro freezes after login on the admin account. The status bar doesn't even appear, nor the desktop icons. Nothing responds and I need to force shutdown to be able to reboot. 
Those are the things I already tried :
- rebooting in safe mode : desktop icons will appear, but everything freezes after a couple of seconds. I believe since safe mode doesn't work the problem is related with the Finder, DS_Store issue, icon issue, or an iCloud issue. So I went to the next step. 
- running the disk utility First aid tool in the OSX recovery tools (reboot+Cmd+R) : It says the disk is OK. 
- running /sbin/fsck -FY in single user mode : the disk seems to be OK. 
I don't know what to try next. Since I really need my computer for the next days, I might go to an Apple store later this week. I would of course be really happy to avoid the costs of that option. 

Does any of you have an idea of what I should try next? 

UPDATE

As Allan suggested, the problem was my drive beginning to fail. I changed it to a ssd and everything went back to normal.
On Apple Support Communities I got a helpful answer I will copy here for others. I don't exactly understand what it does exactly.


  Log in as Guest. 
  
  This procedure will delete certain temporary and
  cache files. The files are automatically generated and don't contain
  any of your data. Occasionally they can become corrupt and cause
  problems such as yours. 
  
  Please back up all data. 
  
  Triple-click anywhere in the line below on this page to select it: 
  
  /var/folders
  
  Right-click or control-click the highlighted line and select Services ▹ Open from the contextual menu.* 
  
  A folder with the odd name "folders" should open. Inside "folders" are several subfolders, each with a two-character name. Drag all the subfolders
  except the one named "zz" to the Trash. Don't delete the subfolder
  named "zz". You'll be prompted for your administrator login
  credentials. Restart the computer and empty the Trash.
  
  * If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination Cmd-C. In the
  Finder, select
            Go ▹ Go to Folder... from the menu bar and paste into the box that opens by pressing command-V. You may not see what you pasted
  because a line break is included. Press return.


I have to mention that for now, it solved my primary issue. However, I'm experiencing some extraordinary slow speed on every app up to now. I guess that this might be caused by the missing temporary files that the system is rebuilding.

Hope this helps somebody!