One feature that I’ve found useful but am often disabling when I have zero need for it is the Handoff feature.
The idea is awesome. You can start something on one device and then pick it up on another.
Start a document on your MacBook and then open it up to the same spot on the iPhone. Very cool. Not always necessary, though.
If you don’t have any other Apple devices, this one is wasting battery life for no good reason as well.
Disable Handoff when you aren’t using it and save yourself some battery life.