You don't have a captive audience. If you assume readers start at the beginning and read straight through to the end, picking up the thread of your argument as it builds, point by well-constructed point, you're going to write the copy all wrong. People just don't read your stuff that way.
Your readers skip around, skim, get distracted, lose their place, come back later at a different place. Which is why repeating yourself is necessary. Whatever it is you want people to do, tell them that thing again and again and again.
Repeat yourself because you don't know if they understood it the first and second times.
Repeat yourself, because you can't be sure they even read it the first and second times.
Repeat yourself because sometimes, even when they read it, it doesn't sink in until they've seen it a few times.
Repeat yourself because you aren't sure what way of saying it is the one that gets through to any given donor.
This repetitive quality can be pretty annoying. It will especially stand out when you're reading closely and carefully: I heard you the first, second, and third times! Enough already!
Don't worry. Be repetitive. It works. It really works.
