Star Ocean: Second Evolution (Part 17) - Field of Courage
The Field of Courage is on a small island to the south of the world map. I found this to be the easiest Field, probably because it's the shortest and the enemies aren't so tough. The thing to realize here is that most of the exits of rooms will lead you back to where you came from. In other words, doors aren't two ways: if you enter a room then leave by the same way you came in, you'll end up further back. It's very straightforward if you remember that.
Enemy-wise, the Otifs can turn you to stone, so Rena's Dispel (or some Familiar-bought Spring Waters) come in useful. The only two enemy parties which should give you major trouble are the set of two Fenrilbeasts (the older-older brother of the Salamander; use the same tactics) and the set of eight Darkcrusaders, which surround you. Try to beat two or three of them near your spellcaster (Rena or Celine), then have them let go with Lunar Light or Light Cross as soon as they can.
Follow the instructions I give exactly; don't stray from the path. From the start, first head left and pick up a Sour Syrup, then go back right to the start. Head to the top left for a Spring Water, then go to the top left again. Pick up the Jeanne's Shield and continue to the top left. Go left from here and pick up the Warrior Statue, then go right to reach the room you were in before. Go right again to pick up a Scyther. Continue to the lower right and get the Mithril Greaves. Go to the lower right and pick up the Stone Check. Yep, that's all the treasure there is, so just head down to end up back at the start. Go out and save if you wish.
Head right twice, then go into the elevator to reach a save point. Save, then head right to get to the boss battle. (Told you it was short!) The Guardian is identical to the one in the Field of Power. When you beat him you'll get another Protection Ring, and (after a scene) the Jewel of Courage. Go back up the elevator, left twice, and down to exit.