What does Swiss cheese, and learning math have in common? Well when we learn math it is a lot like a block of Swiss cheese, we have some holes in our knowledge just like the Swiss cheese has holes in it.
Now these holes do not make up a large amount of the slice of Swiss cheese, and so it is with our knowledge of math we probably have most of the knowledge that we need but there are holes in it.
Unlike the Swiss cheese thou we don't always see the holes in our knowledge. We may be missing only 5% of the slice but that 5% can cause a great deal of heart palpitations, brain freeze and dread.
Thirty years ago I took my first Calculus class. The first week or so was boring, then I hit a hole. That hole has caused so much discomfort, but until just the other day the hole has remained, not fully understanding what it was that I was missing.