Android continues rebooting and 'optimizing' My S5 was running Fusion ROM 5.0.   I downloaded 5.1 and installed using ROM manager.  After the installation, Android continues rebooting and saying "Optimizing app 1 of 8.   Facebook...", then reboots a few seconds later into the same process. 

What do I do to break this cycle and get my phone back?
It may be problem by the rom


clear the data 
clear dalvik  cache 
reinstall ROM 


This may help cause you may have directly the ROM without clearing data



Footnote: Though in Android 5, Dalvik was replaced by ART, parts of the Dalvik stuff are still used (/data/dalvik-cache/arm/*; also see e.g. Should Dalvik Cache be wiped in ART). While in the end, apps will run from native Elf binaries, ART creates those via .oat files. Details can be found e.g. in this Wikipedia article. So don't be confused about "clearing Dalvik cache" here. You could still make sure to remove ART cache by running rm -rf /data/dalvik-cache/arm/* as root via e.g. adb shell when in recovery.