Google's changing its security policy - merging all the various systems it has. Given that Google and Amazon now own everything (seriously, I'm expecting to come home and find a coin-slot on my fridge with an option for Prime Express Delivery), we need to be careful about what we tell them about us. After all, they take all that information and sell it on - that's the business model.
First thing to do is pause your Google History (including Youtube). You can't wipe it, and they'll keep using it for internal purposes, but it's a step in the right direction. Log in to your Google Account, go to google.com/history and press 'pause'. Job done.
My history is so boring: