Struggle

There is always a struggle going on between the forces of Light and the opposing forces—when there is a true movement and progress the latter try to throw a wrong movement across to stop or delay the progress. Sometimes they do this by raising up old movements in yourself that have still the power to recur; sometimes they use movements or thoughts in the atmosphere, things said by others to disturb the consciousness. When a settled peace and working of the Power and self-giving of the being can be fixed in the physical, then there comes a secure basis—there are no more fluctuations of this kind, though superficial difficulties may continue.

Ref :  Letters on Yoga – III