Nice message in my inbox, from a reader of this blog:

Hey Alwin,

I wanna thank you for your tips on “How to sell more stuff to your existing customers“.
I followed your advice and, as you can see, got some spectacular results:

I really needed that “do not hesitate to send reminder emails”.
Without your graph and that beautiful second peak I would never have sent the reminder mail. Was nice to see that with another product, other campaign, the impact is similar.
Perhaps marketing is science after all 🙂