Did you made these (dont forget it''s a Phone and not a Laptop):
-disconnect wifi and internet Data when you not use Internet
-disconnect Location,Gps when you don t need
-disable All applications You don''t use frequently
-choose a Black wallpaper(the screen is 5",so a lot of battery needed here)
-disconnect Autosync and sync manually when you have time to check e-mail,Facebook,etc.
-Use Clean Master .apk to close apps and clean memory
-avoid keeping the phone in the heat(sun,worm places,etc)
-keep display on AUTO brightness or minimum
-choose a black theme for Keyboard ?
If you did so,you shouldn t have any problem.