Restarting Unity desktop in Ubuntu

If your desktop seems to freeze for more than a few seconds, trying pressing together the keys

Ctrl Alt F1

login with your username and password, and type

unity & disown

This will leave your desktop/apps all as they were while fixing the broken state.

To just restart the whole Unity desktop (which is like unto logging out and logging in, discarding your current desktop), instead type

sudo service lightdm restart