As the title suggests really. I have a new MBPr, bought 2 months ago. I never get anywhere near the quoted 7 hours battery life. I attach a screenshot from clicking on the battery below, as well as coconut battery status
The battery doesn't just drain (unless it has quite a major internal fault), look at your Activity Monitor, CPU tab, to see what using the highest CPU cycles and therefore causing the battery usage. Or click on the battery icon in the menubar, it will, after a short pause, tell you which apps are using significant battery.
Apple actually gives a figure of 8 hours, not 7, for your 2014 15-inch rMBPro. Also, notice that 8 hours is not guaranteed, nor does it say you always get 8 hours. In fact, the specs do not say just "8 hours", but does say "up to 8 hours Battery life is very dependent on your usage. Lots of info here: http://www.apple.com/batteries/