If the excerpt given in the original post is any indication, the wording of the passages is probably too general to be of any direct effect but there is some evidence that forming what are known as "implementation intentions" does have some effect in helping direct oneself in goal attainment (http://www.psychologytoday.com/blog/dont-delay/201001/implem...). So it could be that reminding your self to "persist" can lead you to form a more specific intention that does help you towards goal achievement, but you're probably better off just making your own set of implementation intentions and reading those each day.
I'm a fan of implementation intentions and have found them to work well.
There is a good book chapter from
Bas Verplanke called "Habits and implementation
intentions". A pdf of the chapter can be downloaded from http://uit.no/getfile.php?PageId=1935&FileId=312 The chapter focuses on habits and then how implementation intentions can be used to change them.
