If Unity starts behaving erratically or slowly we will probably want to restart the shell, which can be easily done by pressing Alt + F2 and running the command
Another option to restart Unity is to open a terminal and enter:
unity --replace &
at the end of the command we will make sure that Unity does not end when we close our console, otherwise when we do we will run out of shell. If it ends anyway then it will be best to execute the order
using the Alt + F2 key combination.
Sometimes restart Unity it will not be enough for make it work properly again, in this case there is no choice but to log out and log back in to continue working without any burden.
More information – Unity: Using the new launcher design in Ubuntu 12.10, Accelerating Unity on modest systems