A little piece of evidence pointing to hypothesis "Harry had stolen Hermione's body".

"I care enough to make an actual effort" can be interpreted as "I already made an actual effort", and that was the interpretation that came to my mind on the first reading.

Also, this is very interesting:

The most likely prospect for disaster is a powerful wizard who, for whatever reason, cannot bring himself to halt as warning signs appear. Though he may speak much and loudly of caution, he will not be able to bring himself actually to halt.

And earlier:

Harry didn't venture anywhere near the border of the Forbidden Forest, since there was no reason to take the risk. He walked invisibly among the more ordinary life-forms of the permitted woods, wand in hand, a broomstick strapped to his back for easier access, just in case. He was not actually afraid; Harry thought it odd that he didn't feel afraid. The state of constant vigilance, readiness for fight or flight, failed to feel burdensome or even abnormal.

...told Professor McGonagall that he was currently talking to the Defense Professor in the woods outside Hogwarts (just in case anything happened to him)

It looks like Harry will be able to actually be very cautious as opposed to speak about being very cautious.

Maybe this story will not end in a complete disaster.