Most of us have heard stories of how serving in the army makes for an amazing discipline in a person. It seems to be true for most of the world's armies, even the ones that reportedly don't do much active training: a rebel goes in - a confident and purposeful young person goes out.
It's easy to understand the direct reason: the army pushes a recruit through a series of very hard challenges, which apparently break the recruit's spirit, breaking them off of their old mindless habits and allowing spirit to reform under a new paradigm, which includes, among others and in layman's terms, a concept of "whole-assing the thing you deem worthy doing". This is achieved through severe pressure from officers, who take it as their job to punish the soldiers enough to allow for paradigm shift.
Is it possible to achieve the same level of discipline alone, without such a hard pressure from outside? If so, how does one achieve that? Good discipline is without a doubt a desirable trait to achieve.