App keeps closing

Try a reset. Press the Sleep/Wake button and Home button at the same time for ten seconds until the Apple logo appears. Note: No data will be lost

No problem

One additional tip, is to remove any unnecessary apps from your multi-tasking bar to help free-up memory. Do this by double-clicking the home button, then tap and hold an app, and tap the minus sign by any and all apps that you don't need available for multi-tasking. This has helped my iPhone run much more smoothly (particularly handy, because I almost never mult-task and don't need the battery drain, or the memory filler.)

Hello hoppdloop,

Most apps don't actually stay running in the background and therefore don't use any system resources.

Read here > http://support.apple.com/kb/HT4211

Regards