Don't Install if You're Traveling
Are you currently traveling for work or pleasure? This is not the time to install the macOS Sierra update. No matter how much your Mac tells you that this is the time to install an update -- don't do it.
We've heard from users who decided to install a Mac update in an airport right before a flight and were left without a working computer. The same goes for installing this update in a hotel.
Wait until you have the time you need, are at your home or office with a current backup and then upgrade to macOS Sierra.