neotoma just made a really fascinating suggestion in
a post to
snapesupport regarding Snape's use of the Pensieve before each Occlumency lesson:
From what Dumbledore says in Goblet of Fire, the Pensieve is used when one's 'head is too full'. If a Pensieve actually extracts the memories, and leaves more room in one's head for other thoughts, Snape could have been taking out painful memories not to hide them from Harry, but to keep his temper in check long enough to teach the kid.
Up to this point I'd been fond of the idea that Snape had enough wary respect for Harry's potential abilities to want to get his most embarrassing and/or painful memories out of the way so that Harry wouldn't see them; but if that were the case, you'd think Snape would have removed a lot more memories -- I can't imagine he really wanted Harry to see Little Severus crying in a corner, either (or at least, not consciously). But I like
neotoma's idea a great deal, and it seems quite possible that it constitutes at least part of Snape's motivation for borrowing the Pensieve.
Thoughts?