Sentence:  As the historic processes of modernization gradually gain momentum , their cohesion will be threatened by divisive forces , the gaps between rulers and subjects , town and country , will widen ; new aspirants for power will emerge whose ambitions far exceed their competence ; old rulers may <WSD>lose</WSD> their nerve and their sense of direction . 
Meaning of the word marked with <WSD> tags:  fail to keep or to maintain; cease to have, either physically or in an abstract sense