Honestly, there is not really a need to argue back and forth here.
From what I can gather, Istaru is stating that one should strive for perfection but never expect to actually reach it. It is the attempt to constantly push yourself to be better that is the point, not ever actually reaching "100%". By setting a goal that is as impossible as perfection, you will never reach it and therefore always have something to strive for. It is the eternal journey of self-improvement, which I personally feel is a path everyone should try to follow.
I will state that this idea, if I am correct in it, may have been muddled by introducing the concept of accountability which can result in a great many different interpretations and reactions to that word. Some take it to mean "fault" or "blame" which has an inherent negative connotation and often is seen as accusitory, resulting in a negative outlook on the idea presented as a whole.
Shougun is also correct in proposing that there will be things that are outside your control, such as the actions of others. You should not blame yourself or hold yourself accountable for things outside your control. Other people's actions are theirs and the only thing you can control is how you react or respond to them.
So really, the ideas being presented are not in opposition and can and should be sought after in a harmonious manner.
So in summary:
Push yourself to be better and to always strive to learn and improve. It's when you settle for "good enough" that you no longer grow.
Don't beat yourself up for the actions of others, it was their actions and not yours and you can't control their actions only your reactions.
Blame and other such inherently negative actions rarely, if ever, have a positive outcome.
Inherently positive actions such as being helpful or understanding are much more likely to result in a positive outcome.
Funny how that is, isn't it
Holding yourself to high standards should apply not only to your actions, but your reactions to others' actions.
Lastly and perhaps most importantly, we all need to remember that it's a game we play to enjoy, so don't take things too seriously or personally and don't be a jerk. It's easier to have a fun time, when those we're playing with are also having a fun time.