Reddit reviews Destiny of Souls: New Case Studies of Life Between Lives

What you described sounds like an interesting way for a spirit friend of yours to help you out in life. It's possible that some assistance in crucial moments was necessary to ensure your path unfolds as planned. Apparently, your protector has a flair for appearing to you dramatically.

Chances are that the armor is just his personal choice, the role in which the friend wanted to present himself to you this time. Maybe it symbolizes a history the two of you share, or maybe it's armor he wore in an incarnation he enjoyed living.

If he said goodbye, chances are that his role in your life is indeed over, and you won't be seeing him again. Your life is yours to live. It's likely you'll see him again on the other side. :)

You probably don't need to research this further, but if you want to, I recommend this and this.