Why is y battery life is daraining even when its not used?

[AC Question]

I bought samsung J2 on 25th dec 2016. From last 3 days my phone becomes switched off when i wake up in the morning even when there is max 60% battery life at night. I can't understand what the problem is! Please enlighten me

 

[belodion]

What do your battery usage stats, in Settings, Battery, Battery Usage, indicate as the main users of charge after such a drain?