There is an item in this game named the Energy Tank whose function is to fully restore the health of the party. Like most items, it is intended to be discarded upon use; however, there is a glitch in the game involving it's use. Primarily, this item is only consumed during battle! Thusly, if you heal with the Energy Tank in the field, you will not lose it, making it easy to fully restore yourself outside of battle. Note: If you have Pteras in your inventory, they'll be discarded instead of the Energy Tank in the field. If you don't have Pteras, then nothing is discarded and it is essentially a free heal.