Why does my iPhone 4s do this?

Okay so let's say I would be on my phone for awhile n it would have 45% battery left. So I would turn it off and go to sleep then the next day I would go on and it would only have 20% battery? Could it be because I drop it a lot and it got all messed up or does that happen to anyone else? - k thanks.

The reason that happens is because the phone is still on just on sleep.(This is normal for all devices) This happens on my laptop: I put it on sleep and in about 1 hour, the battery is low or even dead. So from now on, i put it on hibernate instead of sleep.So, the point is that you should turn off your phone if you are not going to use it for a while so it won't waste battery. (But also keep in mind that you won't be able to receive notifications, calls, and messages until you turn it back on) I would also recomennd that you shut it off when you go to bed since pretty much all phones create large amounts of radiation, so to just to be safe, turn it off.