This semester I've been directing two independent projects: one M.A. thesis and one undergraduate honors thesis. It's my first time directing a thesis of any sort, and though I've been a second reader on at least half a dozen--and in some cases got pretty intimately involved in the project--being this up-close and personal with another person's thought process has been interesting.
On the most basic level, it's hard to guide usefully without guiding too much, and it's hard not to be disappointed when a smart student nevertheless doesn't quite get what you're saying or go as far as you think he or she could go. I spent a lot of time talking ideas through with both students, trying to help them to recognize certain connections that they seemed to intuit but couldn't quite express--and in both cases it was mildly frustrating to lead them right up to an idea and not have them able to make the final leap on their own.
That's fine, of course, and they both did some good work; when it comes right down to it, a thesis is more a skills-building exercise--a demonstration of growth and mastery--than something that needs to be lovely and perfect in itself. (God knows, this is how I came to see my own graduate seminar papers and to some extent my dissertation.)
So yes: it's satisfying to see students grow and improve and I certainly point out to mine the places where they've grown and improved and I tell them what I'm pleased with. But when you're interested in the project and you've got a restless, tinkering mind, it's hard to know what's good enough, or what's sufficient improvement, when it's somebody else's life and work.
Maybe this is what it feels like to be a parent.