Battery damage can occur when you keep a device plugged in all the time, never using the full range of the battery (I've done this to my laptop). This can also occur if you let the battery sit at 0% (or even 100%) for a long duration. Most current devices ship with a 50% battery charge for this reason.
I am a firm believer of fully discharging a battery at least once ever 4-8 times you charge it, just to avoid "battery memory" issues.
That said, perhaps you have an application that is using more battery than it should, being samsung/android I'm assuming you have a battery monitor application pre-installed (accessible within settings) that will tell you how much battery each running application is consuming. If (for instance) Angry...