I'm sure it's stupid survival extinct that step in .. not anxiety .
if your choosen method is instant and can't be interrupted ,
like a gun shot .. It's always too late to be "rescued" ( like they call it )
then I think you're best shot is when you reach your smoke point ( like I call it )
when you're really angry , furious or in tremendous pain .
when the feeling that is pushing you towards Suicide is too strong that it beats up any stupid wicked instinct .
whatever it is you noticed that often drives you over the edge .
a fight with someone , some thing/person irritates you , .......
if the method needs total privacy not to be interrupted , well you could recall/remember the bad things that you wish to avoid by taking your own life .
and emagine how worse it could get if you backed out .
if that didn't help .
then I think you should dismiss aggressive ,violent and brutal methods all together
because hurting your self is not easy .
N and SN may feel like ingesting a meal or a drink = somethings your survival extinct is not equipped to fight involuntarily ( unlike fear of heights , electrical shocks and burning reflex reacts , ... )