In case your laptop is never used by anobody else, then I see no use of Guest Session. Guest session is only necessary if you let other people to share your laptop. In my case I never let anyone to use my laptop, hence for me my user account is enough. So I removed the gurst session from my device.In order to remove the guest session, do following things in your terminal:
  • First open your terminal:  CTRL+ALT+T
  • Then type: sudo gedit /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf
  • In your text editor simply add this line of code allow-guest=false
Now save your configuration file, Close it and restart, this is what you will see: