Battery drain problem

[Messilio]

Hello i have a question please i have a Sony xperia z3 d6633 and i feel that the battery is not as strong as i expected it gives me 10 or 11 hours and the screen time on is 6 or 7 maximum and i am a heavy user and stamina mode always on and brightness is just above the middle is it normal? Do you have any advice? Plus, it never ever survived a 24 hours even i used it lightly. Thank you!