Stationary blur 
As for the focussing if your capable and know what your doing you can easily adjust the flyback to produce a perfect clear sharp picture.
Wrong, it is never perfect and that is the point. A pixel that exists conceptually as a discrete rectangular area within your framebuffer is mapped to a diffuse point on a screen by an analogue system that is highly susceptible to electric and magnetic fields. Everything about it, from it's position, shape, brightness and even it's colour are affected by multiple, nonlinear effects. You will never get the same combination of these effects from one day to the next. Your CRT display literally is never the same twice.
Contrast this scenario to LCD, where you have well-defined rectangular (usually square) pixels that aren't susceptible to any such effects.
Also if your willing and capable to take the time the coil on the neck of tube can be adjusted to get near perfect convergance for all three colour guns. Any convergance problems still left over can be eliminated with the use of small thin magnetic or metallic strips you carefully place at strategic points on the actual tube itself even under the coil.
Ahem:
'Particularly blurry' is a bit like saying, ok it's a 100 watt bulb but it really only gives off 60 watts, doesn't cut it with me Im afraid...
Substitute 'particularly blurry' for 'near perfect'.
Basically, what you have described is a trial and error manipulation of the fields around your monitor. If you move your monitor, the necessary placements to counter things like the prevailing magnetic field direction all change too.
