This is Dale Grote's advice in chapter two of A Comprehensive Guide to Wheelock's Latin. The terrifying concept in question is the inflection of nouns and adjectives into six different grammatical cases. Simply put, nouns have different "inflected" endings depending on their grammatical function, and adjectives are inflected to match their noun.
What is really terrifying is that some of these inflected endings get recycled, so the same word could have more than one grammatical meaning. As an added bonus, the endings are recycled slightly differently in the singular and the plural. So puellae means of the girl (genitive/possessive) and to/for the girl (dative/indirect object) in the singular, but the corresponding forms in the plural are different (puellârum and puellîs, respectively). Puellîs is also recycled in the plural as by/with the girls (ablative/adverbial), and puellae makes a reappearance in the plural as girls (nominative/subject), or girls (direct address, as in "You go girls!"). No wonder inflection has gone out of fashion. I wonder if Latin represents a transition from greater or lesser inflection? Were primitive languages fully inflected or was Latin (among other inflected languages) an attempt to improve grammatical clarity through greater inflection?
Grote is right, though, it's really not that terrifying after a while if you practice. And practice. And practice some more. As Professor Wheelock says, repetîtiô mâter memoriae.
