iPhone batteries can be sneaky. The battery life on your phone might last the entire day, or it might last for only a few hours. Of course, a lot of it depends on how glued you are to your phone, but there could be another reason why your phone loses charge quickly: your apps.
To find out which apps are draining the battery on your iPhone, go to Settings and tap Battery. The apps you've used in the last 24 hours will pop up with a percentage of how much battery life each one has used. There's also the option to see how much battery each app has used in the last seven days.
The apps with the highest percentage are obviously the apps you use the most. To find out exactly how many minutes (or hours) you spent using each app, tap the clock button in the upper right corner. Underneath the name of each app, you'll see the amount of screen time vs. background time.
This might be a good time to regulate how often you use those apps (i.e. Instagram and Facebook), but that's a whole other issue that you probably aren't ready to discuss.
To avoid your apps draining your battery in the background, kill each one after you use it by double tapping the Home button and swiping up.
Aside from cutting down on your app time, you can also save power by reducing your screen's brightness and by turning on Low Power Mode to prevent apps from refreshing in the background.
Hopefully after making changes to your app usage, your battery will last all day — or at least until you're near a charger.