We can use the logical side of our brains too

Ok, those sample sentences were over the top.  But I bet you will not soon confuse your subjects and possessives.  However I want to go a bit further in our discussion about case.  When we say case is the role a noun has in the sentence, and when we note that Latin tips her hand to these roles with specific forms for each noun, we are left to ask a not-so-obvious question:  how do we deal with these forms?  You see, we are not used to this many-forms-for-one-noun idea in English.  What are we to do?  Let me suggest two possibilities as we move along.
First, we must commit to a lot of practice using nouns in all sorts of uses.  We meet this practice in reading sentences and stories where we have the basics of the vocabulary down pat.  Reading over and over again.  Reading to friends, former friends, neighbors, pets, you name it.  Just read.  And writing, too--writing sentences, stories, cartoons--you name it.  But above all, read and write!  And as we do these activities, we must be open to correction and think about why we are corrected.  With time and practice
But second, we can use the logical side of our brains and note that these forms fall into groups.  Words like ancilla, cibus, and canis are used when we make subjects whereas ancillam, cibum, and canem are used when we make direct objects.   We can name the groups--which language does--with the specific case names nominative (for when a noun is a subject) and accusative (for when a noun is a direct object).  Knowing these names is not a substitute for knowing what the words are doing--in fact they are often a hinderance--yet being able to talk about what the words are doing can help us focus on what is going on.
So let's do both.  Read much.  Write often.  And talk about how we do it by describing the words we use.