1) Pause game if you think your going to be defeated whilst in battle.

2) Select (equip) now resume game at the beginning of the battle, and all your energy should be restored.

Mar on the ship:

1) Go to Zeus and Sephy

2) There will be a choice to let them join you, just say no!

3) You will see Mar once you go back to the cabin area.

Unlimited life

Just when you are about to die, choose equip on the main menu and you will begin to battle once more with a full life.