Warning: Possible spoilers follow.
I was exploring the Lanaryu Sand Sea the other day. There is a pretty epic roller-coaster-like mine cart track there. At the end of it there is one of those log stumps that you can sit on and heal yourself.
Spoilers end here.
I was down to about 22 HP out of 48 (that's five and a half hearts out of 12) so I decided to take a quick break. I then saw some monsters come out and try to ambush me.
That didn't exactly work, though, because Fi seemed to have an issue with my quick break. The funny thing is, when she started telling me off, she actually paused the game temporarily, but I was still able to heal myself whileshe was talking to me. Next thing the monsters knew, I was back to full health.
Fi win :D