Macbook Pro Battery

I bought a MacBook Pro (Retina, 13-inch, Mid 2014) sometime in August 2014, and have been using it. Lately I notice the battery has been drained out faster than Apple claimed to last 10 hours. In fact, the battery is draining faster than I expect i.e. it only lasted not more than 5 hours. What I used the MBP for surfing internet and normal iWork (Spreadsheet/Pages/Keynotes), no video or movie...but the batter does not last more than 5 hours. Can someone help me on this.

Anyone can help on good practice on battery. Whenever at home when I use the MBP, I always hooked on the power supply, is this a good practice. I only rely on battery whenever I am outside the office.