Meh. Read up to something like, page 12... I'll see if I have time to read the rest. But anyway. I guess it's because I play the easist difficulty and I cheat by saving very often (^^), but I very rarely, if ever lose troops... Psi being a different thing. I would advice you to go to
www.xcomufo.com and read the strategy guide... It's very good. That is, if you don't want to play the game without any help.
Ps. Just to make this clear:
X-Com: UFO Defense is the US title
UFO: Enemy Unknown is the European title
X-Com: Terror From The Deep(s?) is the sequel
X-Com: Apocalypse is the third game.
But I guess you knew this.