Everyone has a tipping point, a Berserk Button, a threshold of shock and joy and weirdness that once crossed collapses all emotional reserve like a "Fawlty Towers" Plot. Some, however, have such an exceptionally high threshold that they'd probably greet the impending collapse of the universe with the same equanimity as cold tea.
Characters with Nerves of Steel are of steel in the same way a physical body can be Made of Iron — they are nigh-unshakable.
Those who have Nerves of Steel think when times are tough. They make decisions efficiently; they push their emotions aside, and so their decisions are not overly affected by them. They may be The Stoic, or they may be perfectly normal emotionally. Either way, their minds are never shoved aside when their emotion is. It is always thinking, a weapon as sharp as a sword. Characters with Nerves of Steel aren't intimidated by screams from those with a Hair-Trigger Temper, won't get upset if their Evil Plan is foiled (this is a morality neutral trait), they aren't likely to burst into tears when it turns out The Hero is Not Quite Dead and got better, and very probably won't even raise their voice to the man who murdered a Bus Full of Innocents unless the sound of their righteous ass-kicking is loud enough to require it. Even happy news and emotions aren't likely to cause exaggerated reactions of joy (though they probably enjoy a nice hearty laugh every now and then). When captured, they are defiant and likely planning their escape.
Reasons for this demeanor vary. They probably have Seen It All, are naturally Spock-like, have an iron-clad Stepford Smiler facade (though on the inside they probably are banging their head against the cage) or emotionally can't be made to feel extreme emotion, such as the Tin Man. This doesn't count if the character is an Empty Shell since there isn't anyone home to excite. The Extreme Doormat may count depending on the individual case (some are just too listless to care at all, not requiring any emotional control at all). Affably Evil villains and The Chessmaster are always composed as a result of everything going according to plan.
Even if this person doesn't have Psychic Powers, his incredible self-control often makes him resistant to those who do.
In short, someone with Nerves of Steel is immune to the Heroic BSoD, Villainous BSoD, and Villainous Breakdown. God help us all if this proves untrue.
A good trait for a Badass Bookworm to have, at least if they want both halves at the same time. Note that nerves of steel may be hard to distinguish from Tranquil Fury at times. Previously susceptible characters may suddenly develop Nerves of Steel when it's The Last Dance. Showing a Stiff Upper Lip is a good way for a character to convince other people that they have Nerves of Steel. Compare Heroic Safe Mode, where the emotional/thinking part of the brain "shuts down" to allow for instinctual survival mechanisms to work unclouded by emotions. Post-Victory Collapse is when a character fakes having Nerves of Steel, but breaks down as soon as the danger passes. Not related to Balls of Steel, which is more literal, and has nothing to do with Boobs of Steel either. Contrast Nervous Wreck.
