Mating

Traditionally, once a Na'vi male has passed the tests on the path to manhood and has been accepted into the clan as an adult, he is not only allowed to make his bow from the wood of the Hometree, but he is also expected to choose his woman. After the woman has been chosen, the new couple are mated before Eywa.
Jake Sully chooses Neytiri to become his mate, and she accepts and mates with him under the Tree of Voices following his acceptance into the Omaticaya clan as 'One of the People'.
Once Tsahaylu is made between the couple, the ultimate in intimacy, pleasure that is unfathomable to humans, causes the somewhat unwillful sharing of the couple's good memories, and is a sign of Eywa's acceptance. If a couple can be foreseen to not have a pleasant or happy future, Eywa has been known to reverse the feeling produced by making Tsahaylu, a sign to the couple that mating would only, in simple words, ruin their lives together, and therefore prevents the mating, because of it's life-long span. After the resulting embracing and kissing, the couple is sent to sleep by Eywa, and the two dream hintings of their future together. The couple will experience the pleasure of Tsahaylu from the moment of connection, until they awaken and have completed mating, when they disconnect and return to the clan, mated for life.
more after the Jump...