I managed to beat the final mission. Actually, the final mission was the easiest. On pretty much every other mission, I came out with less than 75% health. On the final mission I didn't even lose all my armour. Also, when I started playing from where I left off last, I somehow glitched my controller, so I couldn't actually shoot. So I had to restart the game, and that pretty much fixed it. Also, mines are evil!!