How difficult it is to find problems in my own paper!

After revising my thesis for several days, i picked out one of my earliest editions to see whether i can find those problems again, to my dispointment, every sentence seems to be fluent to me, how difficult it is for one to find problems in his own papers! In these days, i asked several colleagues to read the thesis together with me, and found a lot of problem, but i can hardly find one by myself!