If you have never owned an Android device before the Fire, then you might not be aware that apps often don't really close when you exit them. If you are not careful you can wind up with a lot of running apps that can become a drain on your battery and slow down the Fire's performance. There are apps available that can help manage this issue.

Another way is to manually stop unnecessary apps from running by pressing Quick Menu --> More --> Applications then select Running Applications in the Filter by field. This displays a list of all currently running apps along with how many processes and services each uses.

To stop an app from running, select the app from the list and on the screen that is displayed press the Force Stop button.

Some of these probably should be left running like Settings, Amazon Device Client Platform, Kindle Keyboard, etc. But some are simply apps you opened hours ago and thought were closed when you exited them. Use your judgement and close the unnecessary apps and this will help battery and power performance.