I tend away from terms like 'calm abiding' because i don't even know what it means, and contrary to popular opinion, breath awareness isn't necessarily calm. It can be, and ideally should be, but if it's boring, frustrating, uncomfortable, impatient and otherwise uncalm, then you can see how an inane, reactionary mind creates stress - which is not optional as such - but through recognition of it being unreasonable and futile, it tends to lessen a bit over time.
If indeed the wild mind is stressing out somehow, leave it to its devices and become more determined about feeling the breath. That way the wild mind learns that cannot control and compel you. It recognises what used to work no longer works, and moves its tricks to deeper levels which as yet you might not be conscious of.
The ego is deprived of 'fuel'. You stopped giving energy to it when you 'just observed'. It starts to freak out, so you can reasonably expect meditation to be rough sometimes. Since you know your 'just observe' is disruptive in this way, you understand, 'oh this ego is being starved out of hiding and is trying to keep control'. It wants to keep that position of 'me' and does everything possible to rule the roost. It brings aches and pains to the body, some emotional turmoil and negative self-chatter because to remain the imposter of 'me', it has to keep you in a reactive, distracted state - which we can recognise as aversion, boredom, frustration, impatience and all those things etc. Craving a 'special experience' is also a good trick. That's probably the best trick it has.
If those sorts of reactionary feelings come up for you, good, it means wild mind is being tested, or it's testing you - either way of conceptualising it is fine. If it learns it has no power to compel you, what it's doing its not working, it stops doing those tricks. Hence the mind becomes less wild - and therefore calm.
Don't start thinking this will be calm or not calm. It so happens that it tends to be mostly calming so it's generally quite pleasant, but when the mind does get wild, and it will get wild, be determined, even more determined, to only feel the breathing. If the inner-voice is like 'I don't feel like it' etc. recognise the negativity and be like, I see you wild mind, and you are not the master.
In the formal practices this is called 'Strong Determination' (google it). And that's an aspect of the 8 path 'right resolve', 'right motive' or something like that, and also pertains to 'right effort'.
I just say after some months of refining breath awareness one extends that observation to full body awareness. The scan method mentioned in the article is the best because it covers every part without missing anything. However, I would recommend doing breath awareness with the sort of resolve I alluded to for maybe 3 or 4 months, and at some stage, you start to feel lighter feelings in the overall body. Ants crawling on the crown, forehead pressure, tingle all over, waves, vibrations and/or any sorts of feelings, as you experience them, that are less hard, dense and solid physically, and more subtle and dynamic. When subtler feelings start, I'd remain with just breath for another month or so until it's common and established - and that's when I'd start extending the observation to the rest of the body.
The other thing is, with breath awareness as I describe it, your growing ability to focus microscopically and sustain long enough attention span is really needed for progression into body awareness... but I can feel my own tendency to be overly pedantic kicking in here so I'm dropping this and letting it be as it is
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Yea - more to 'calm' than one first thinks.