1. Open a Terminal by CTRL+ALT+T
2. Type xrandr and ENTER
3. Note the display name usually VGA-1 or HDMI-1 or DP-1
4. Type cvt 1920 1080 (to get the --newmode args for the next step) and ENTER
5. Type sudo xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync and ENTER
6. Type sudo xrandr --addmode VGA-1 "1920x1080_60.00" and ENTER (replace VGA-1 with your display type (step 3) like HDMI-1 or DP-1)
7. Now close the terminal and go to Settings >> Display settings and change it to 1920x1080
Enjoy FHD.
------------------------------------------
> For integrated displays:

goto your terminal and type vim ~/.profile ENTER
Paste in the shell command from step 5 and 6, then save.

> For external displays:

create a script called external_monitor_resolution.sh in the directory /etc/profile.d/. using sudo vim /etc/profile.d/external_monitor_resol.sh.
Paste in the shell command from step 5 and 6, then save.
(Note: if using sudo would require you typing a password, your system might freeze on startup while waiting for you to input a password. So when pasting do away with the sudo) 
Something like this:

xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
xrandr --addmode VGA-1 "1920x1080_60.00"` and <kbd>ENTER</kbd> *(replace **VGA-1** with your display type (step 3) like **HDMI-1** or **DP-1**)*