A little old now, but I just noticed this comment. My recollection of the dentists words were that it increased your life expectancy by two years. That is, if you were guessing how old someone would live, knowing that they flossed would put them at two years above an average person. In other words, there isn't necessarily the slightest bit of causality in this assessment. I still find this sufficient motivation to floss, so I don't care. It would be a good idea to not take this on faith if you were interested in the truth, rather than in just motivating yourself to floss.
Edit: the other thing that helped convince me was the dentist telling me that the bleeding you get when you start isn't that you haven't developed calluses or whatever, it's that your gums are swollen/irritated due to bacteria living off your teeth. Getting past the bleeding is a sign that your flossing is working and gums are no longer irritated.
This is the public group instrumental rationality diary for the week of July 9th. It's a place to record and chat about it if you have done, or are actively doing, things like:
Or anything else interesting which you want to share, so that other people can think about it, and perhaps be inspired to take action themselves. Try to include enough details so that everyone can use each other's experiences to learn about what tends to work out, and what doesn't tend to work out.
Thanks to everyone who contributes!
Academian put up a wiki page with links to the prior May and June threads for reference. Good idea, thanks!