It means that you had a deep understanding for a few seconds, and then lost it. Or that you got trapped in the same confusion as the author, absorbed what made it seem appealing, and then "corrected away" the confusion.
To determine which one happened, try the following:
Eventually, you should be able to either gain the understanding, or recognize where the error is.
This is an excellent diagnosis, and those are excellent suggestions for really learning the material.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.