similarities and dissimilarities in the words of the sufis up to 7th century

talking about ego, in the sufis’ works, two terms of “endeavor” and “austerity” have been sometimes used focused on each other and sometimes alone. did they have similar definitions and positions in sufis’ opinion or had they been different from each other? we claim that “endeavor” and “austerity” had had different positions and of course different definitions in old texts.  it was made clear, after accomplishing present research that the sufi authors had explained these two issues apart from each other in their instructive books on sufism; but most of them used “endeavor” and “austerity” with similar meaning and focused on each other when talking.