It is a somewhat complex sentence, and I had to read it a couple of times myself. To understand it, separate between the commas... I am still afraid of missing something if I forget that, as my father snobbishly suggested, and I snobbishly repeat, a sense of fundamental decencies is parcelled out unequally at birth. The main part of the sentence is on the first and third lines: I am still afraid of missing something if I forget that ...a sense of fundamental decencies is parceled out unequally at birth. And really...the main point the author is making is: a sense of fundamental decencies is parceled out unequally at birth. Regarding why the author is saying he is afraid of missing something, we need to look at the context of the paragraph. My guess would be that the author is saying: I have to remind myself that not everyone has the same sense of decency. Hope that helps.