Survival instinct is a message: "I just can't." Because of this message, one aborts an attempt, or never attempts certain methods at all.
The message may or may not be related to the method. If it is related to the method, one can conceivably suicide by a different method that is personally agreeable/non-fear inducing to them to attempt, and to experience without aborting, due to rapid loss of consciousness. If the message is motivated by pure survival instinct, it will arise in relation to any method, regardless of peacefulness, and one will be either prohibited from attempting or will abort any attempt.
An imminent threat that is worse than any fear of the method or its outcome will override the survival instinct, and change the message from "I just can't" to "I can." The threat must be perceived as worse than fear of the method and/or death, thus turnining suicide into an act of self-preservation and therefore survival.