i cut my iphone 4 jailbroken with evasi0n off and after i powered my phone back on i lost my apps. what can i do to get them back?
It sounds like you had a tethered jailbreak. If this is so you will need to run it by your jailbreaking program again on your PC/Mac and then it should be working again.

This issue does not happen when you do untethered jailbreaks.