A term from the anime series GUNDAM SEED
Some humans have the special ability to go into something called Seed Mode, in which they become extremely superior at things they do such as Kira who becomes a great pilot of his Gundam when he is in Seed Mode. No one knows for sure how this is triggered and who is able to trigger this special mode, but as exhibited by Kira, it seems that it is initiated through some type of strong anger which caused him to go berzerk.
Offically, the definition of SEED is: “A factor that determines the course of a species' evolution. The existence of the SEED factor has yet to be proven, and it remains a subject of intense controversy in scientific circles. But in theory, those who possess the SEED factor have the ability to advance to the next stage of human evolution - an ability unrelated to whether the carrier is a Natural or a Coordinator.”
However, I propose that the theory behind SEED mode, it's true purpose, is to allow those who possess it to see possibilities (the 'future', or 'outcome'), the different ways and results of the actions taken. It is the reason why, when pilots use it, they can always win by seeing the best strategic move to make in the MS, should I fire at the enemy with the rifle? Or should I block his attack and come at him in the ensuing dust cloud with saber drawn? Another way of saying it, SEED is the gift of insight..to see as I said, different possibilities. It is also my believe that this is all triggered by a sudden surge of emotion as well. Athrun and Kira always enter SEED in the worst part of a fight and they are able to quickly analyze the situation and see the best way to win the fight, especially if they feel anger. Lacus was speaking about the war and the future of mankind when she went SEED, most probably, because she saw the possibilities of a future without war and hatred and she felt intense hope. Cagalli, when she went into this mode, witnessed the deaths of the Astray pilots, I conclude, because then she finally saw what her father was trying to teach her about death and war and also her strong sadness. Also notice, where the producers decided to place the SEED animation, or 'trigger event', in the eyes! And unless we can see the possibilities of our own future, how can we expect to ascend to the next stage of evolution? Of course, this is all fan opinion and until someone from the makers officially recognize this it should be treated as such.