Rand & Nynaeve: A Study in Resolve
Rand drags his wounded father through the woods taking the majority of the night to make a trip that both had made twice earlier in a fraction of the time. Despite being practically petrified with fear, Rand is single-minded in his determination to get medical attention for his father. Despite fear, hunger, or weariness, Rand manages to trudge along - a very physical embodiment of self-reliance. Those who have completed an Ironman, run a marathon, completed a Tough Mudder, or any myriad of similar competitions can relate to that point that runners call "The Wall". A tiredness so profound that it becomes a crucible to place one foot in front of the other and just keep moving. When I first started running, my dad often reminded me to "Just keep moving. Slow down, slow down some more; but don't ever stop." The ability to focus through pain and tiredness is why so many entry programs for military special operations involve feats of physical endurance: it challenges body and mind simultaneously in a minimal cost/maximum effect framework.
Mental toughness goes beyond dragging yourself through the mud for hours at a time. It's also critical when making, and sticking to, decisions. Nynaeve, despite her legendary temper, is a competent healer:
Yes, I am. I know what I can do with my medicines, and I know when it's too late. Don't you think I would do something if I could? But I can't. I can't, Rand. And there are others who need me. People I can help.
Nynaeve to Rand, The Eye of the World, p. 79
More critical to this particular discussion is the emotions that flash across Nynaeve's face leading into her reply to Rand's desperate plea for aid:
Pain twisted her face, but only for an instant, then she was all hollow-eyed resolve again, her voice emotionless and firm.
The Eye of the World, p. 79
When operating with finite resources, it's critical to make decisions that provide the most impact or the most options. In times of duress, it's imperative to stick to that decision. Being indecisive eventually allows the situation to control your actions, reducing what was a multitude of options to a single one; usually one of the more unfavorable ones. Conversely, trying to help everyone may yield a spike in short term individual happiness at the expense of long term united success. This isn't to say that building relationships isn't important; it's absolutely crucial, however, relationships are only one factor of many in the decision making system of inputs. And sometimes the importance of the mission vastly outweighs the team's feelings.