(1) Pscyhological aspects and challenges involve the urges one could resist or submit to perform premature moves, the ability to maintain one's attention span and the ability to maintain initiative. For example, imagine an opponent who is trying your patience by stalling and feinting or keeping the initiative (that is, having you submit to his domination by making you wait for him to attack and to give you a reason to respond) while not using it and waiting for you to lose your patience and act prematurely, opening yourself to master strikes, ie. one hit one kill deals if you don't counterattack properly, with very little room to break off and retreat if you don't know how to respond. At the end of each turn and based your actions or inaction, you get cumulative increases (or decreases) to a few derived stats dealing with these.
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(3) Commitment is how much effort and power you dedicate to any single action, and how much of a strain they become on your status. Without fully committing, you could be baiting or feinting the opponent to think you are giving an opening, you could be stalling to try his patience, you could be searching to get a sense of what your opponent might be thinking through his responses or, you could just be unsure of what to do (this last part, "being unsure of what to do" has an actual place in the system based on "Indes"). Commitment also dictates how easy and safe it is to change from your course of movement (a matter of momentum, when applied to real life) and the level of fatigue involved.
That probably sounds complicated but its application in the system is based on very simple and straightforward checks, between your Strength and your Endurance in the case of fatigue for instance: You assign as many Strength points as you have and wish into your actions and when the Strength you commit into your action exceeds your Endurance, it's a cumulative increase on your fatigue but can "cool off" if you refrain from straining yourself again for the next couple moves. When your fatigue exceeds your Endurance (possibly by performing a series of highly or fully committed attacks without breaks), the fatigue increase becomes permanent. When your fatigue permanently reaches or exceeds your Endurance, you become exhausted - but not collapsed... yet).
(4) Initiative is a little more than physically being in the offence or defence. One can hold the initiative while letting the opponent act. I explained this a little in the example above. When holding the initiative, you are in the dominant position, leaving the opponent in an uncertain state of mind, making guesses and trying to figure out how to win the initiative back from you.
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For instance, every character has an Impulse pool that fills up at the end of every turn without a real engagement and further up when subjected to weakly performed single engage-and-breakoff attacks (which don't count as a real engagement) intended to probe or harrass. It's derived from a Will Power attribute (in the same league as Strength and Endurance) and experience. Larger the pool, more patience and self-controlling a combatant is.
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When an encounter drags on in uncertainty, several turns passing without a real engagement and with lots of probing and harassing, these pools fill up, obviously. When you have a full pool, you must roll against the impulse at the end of every turn to stay focused and to refrain from making premature, "impulse" attacks. At that point, your mental fatigue increases whether you pass or fail an impulse roll at the end of a turn, bringing penalties to observation and Indes. Thus, you need to stay sharp. If you have the initiative, this is softened up a little bit (one of the reasons you'll want to have the initiative).
