When I'm trying to double press my home button, the phone goes into a 'safe mode' pleas help me!!!

I was running an app and I tried to open the apps bar at the bottom, but the loading star appears and the phone reports entering into 'safe mode'. It says something about cydia, a program i haven't used but once, a really long time ago. how can i exit the safe mode? should i reset my phone? iphone4