Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 3
It [the coming of disturbances] is not the result of any pressure from above. If there were nothing coming from above, there would be no peace and clarity and the disturbances would still come and come more often.
The cravings once belonged to the vital physical, but when there is a sufficient force of peace in the being, then they go out and the vital physical is free and under the influence of the 
quietude. The forces of disturbance do not belong any longer to the personality, but although they have gone out, they wait in the atmosphere and, if they get a chance, try to come back and resume hold of the exterior being so as either to break or, if they can no longer do that, cover up the inner peace. Because the physical vital has been accustomed to respond to them for a time willingly, now unwillingly, they are still able to make it answer to their vibrations. The peace and clarity must acquire such a force that they will remain even if these forces come back – then there will be the phenomenon of the inner peace remaining undisturbed in the inner being even while the outer is superficially disturbed. This is a well-marked stage in the progress. Afterwards a force can be brought down strong enough to fill the outer being also with so strong a peace and clarity that the disturbances can no longer enter there. One may feel them still sometimes in the atmosphere but is no longer touched by them at all.