It's astonishing to think that only a few years ago we used to live without having around the clock access to our e-mails, social networks and Wikipedia (which is always important when arguing in the pub). The trouble is that unlike the old Nokia 3310 bricks of old, batteries don't seem to last as long as they used to - rather than charge once every few days. If you're an iPhone user you'll eventually find yourself plugging in to charge whenever you're near a socket, worrying that you won't ever find power again.
So is there anything you can do to make the battery anxiety better?
Close apps properly
If it isn't absolutely essential then consider closing your apps. Some apps that you've opened will often run in the background to carry out non-essential tasks will can use up power.
To close an app properly, double-press the home button and your iPhone will show you currently running apps. In iOS7 simply swipe up on the screenshot of the app to close it fully. If you haven't upgraded yet, press and hold on the app's icon and a small cross will appear on the icon - press this to stop the app.
Switch off Background App Refresh
If you have iOS7 then it might also be worth switching off "Background App Refresh" - which enables apps to refresh their content even when not being used. To do this head into Settings, then General, and then you'll see the controls for Background App Refresh. You can either switch this off for all apps, or switch off individual apps, if you know they're particularly draining.
Watch out for GPS usage!
Perhaps the biggest single drain on your battery is likely to be location-based services. If you spot the little arrow in the corner of the screen then be aware - your phone is connected to the GPS satellites and is rapidly wasting all of that battery. So try not to use Google Maps too much, and if an app asks if you'd like to enable location services for a given app, definitely give it some thought.
Switch off 3G
If you're really worried, consider switching off 3G and stick with the slower but less consuming GPRS instead. If you live in a rural area with patchy signal, you may not even notice the difference anyway. Heck, you could even switch off all data if you want to pretend it's 1997 again (perhaps watch some videos of Tony Blair and Friends before you do, to get in the mood).
Switch off Bluetooth and Wifi
If you're not using bluetooth and wifi - switch 'em off. I can't stress this enough. If they're not being used, the radios inside the phone are still on, still constantly searching out for networks and devices to connect to, which will use more power completely pointlessly.
Turn down the brightness!
Arguably the biggest drain on a smartphone's battery life isn't the 3G, or the music playing - but is in fact the screen. Making that panel glow brightly all day is hard work for your phone, so why not do it a favour and decrease the brightness of the screen?
Switch off notifications
Do you really need to know every time someone likes your post on Facebook? Or do you really need to play your turn in Words With Friends immediately? Every time your phone receives a notification it will vibrate, play a sound and the screen will light up for a few seconds - each eating a tiny little bit of power each time. You can manage which apps can send you notifications by going into Settings and then Notification Centre.
Similarly, if your phone automatically checks your email every few minutes, consider switching this off or decreasing the regularity. Do you really need your emails refreshed every two minutes on a sleepy Sunday afternoon?
Finally, if worst comes to the worst, then it might be time to switch to airplane mode. Sure, no one will be able to contact you (which might defeat the point of a phone), but it will mean your phone lasts that little bit longer, and if emergency strikes, you'll still have some battery left.