You can not fix your user account from the guest account for a variety of reasons.
The guest account does not have sufficient privileges (no root access).
Even if you gave the account root access it is confined by apparmor.
You need to boot to recovery mode and identify the problem.
From https://help.ubuntu.com/stable/ubuntu-help/shell-guest-session.html
The Ubuntu Guest Session feature provides a convenient way, with a
high level of security, to lend your computer to someone else.
...
A guest cannot view the home folders of other users, and by default
any saved data or changed settings will be removed/reset at logout. It
means that each session starts with a fresh environment, unaffected by
what previous guests did.
I can not find the details of the guest apparmor profile on the Ubuntu wiki at the moment, but the guest session is too limited to help resolve your problem, whatever it may be.
I suggest you start a new question describing the problem.
/home/$USER/.xsession-errors*
. Did you at an point use "root" or "sudo" to access graphical elements? What doesls -l .Xauthority
show? – Rinzwind Feb 14 '16 at 13:15Ctrl+F2
, can you login with your user account? If yes, dosudo apt-get install awesome
, thenrestart lightdm
and you should be able to pick a desktop environment. – Thomas Feb 14 '16 at 13:56