That's why theres a difference in healing and gaining energy.
Q: What is the difference between “Heal X Energy” and “Gain X Energy?”
A: “Heal X Energy” removes X damage already dealt to a Creature this turn. “Gain X Energy” adds X Energy to a Creature’s current Energy total.
Implies that if you heal energy, it can only go back to ur max energy; if you gain it it can increase the maximum. So that'd be reset aswell, since it says "this turn". So im guessing if your creature doesnt die in the battle then it's energy gets reset to the default on the card.
Danians: Ants with GUNS!!