Perhaps the low point was when, dashing towards a stadium in Tianjin for a Stefanie Sun concert, we were pelted with trash lifted off the ground by strong gusts of wind.
Perhaps it was when, after lugging 100kg of bags to the station at the crack of dawn to catch a 550 yuan (S$110) train to Shanghai, my usually organised sister realised that she forgot to bring her passport.
Or maybe it was when, after carrying a stroller up and down thousands of stairs to get to the obsessively guarded Tiananmen Square - a stunning, wide-open expanse whose sense of history is as palpable as its lack of sheltered places - the heavens opened and it started to pour.
Or maybe the deepest troughs were less dramatic moments. Like the equal parts relief and self-loathing we felt when we relented and changed the baby's soiled diaper just on the train seats. No one batted an eyelid, but we knew we had let Non-China humanity down.
Earlier this month, my mother, sister and 15-month-old niece came to visit me in Beijing for a holiday. And it was a great holiday, insofar as the word "holiday" is defined as "a series of events where nothing goes right and a haze of anxiety hangs over every proceeding".
As it turns out, when you are travelling with a baby, that is indeed the universally accepted definition. When you're travelling with a baby, concepts cease to exist, such as "packing light" or "a four- hour window uninterrupted by the light but unmistakable stench of baby s***".
The baby is adorable, of course. But after a couple of days - and I say this as someone who would give my life for this child - it ceased to be adequate recompense for the sheer, endless tedium of ensuring her existence.
Prior to this holiday, I was in that naive group of people who would wander in and out of my sister's day to coo at how cute the baby was and then exit blithely back to our unencumbered lives.
That group was great and I missed it. Especially when, a week into the "holiday", it felt like the only activity I ever did was folding and loading, unfolding and unloading, the stroller into various vehicles. I had been doing it so repetitively that it felt like I was damned to continue doing so for all eternity.
At some point on the train ride to Shanghai, when the baby was mercifully asleep, my sister and I broached the topic, as frustrated RGS girls are wont to do, of why everything was going wrong.
She was the one who forgot to bring her passport, but I knew that I shared some of the blame.
I had planned our holiday like the baby was just a delightful extra piece of luggage. Like it was just us Chang women, as always, having a good time together with a new plaything. I forgot - or did not want to remember - that a) we would be travelling in China where the ether swirls with an insidious agenda to thwart your every move and b) there's a baby.
So the itinerary had us dashing from city to city, hotel to hotel, packed with early morning train rides and three or four activities a day.
My sister aided and enabled this self-delusion in the planning stages, partly because she is also, 15 months in, still clinging onto the possibility that life doesn't have to change THAT much when you have a baby.
That most of the good things about life before would remain while this additional amazing thing brightened it.
That through sheer force of will and stores of competence and efficiency, baby would only add, never subtract.
("Hah!" says every parent reading this as they roll their eyes - to which I say, don't pretend you've never been here.)
What this holiday ended up being, for me anyway, was a sort of reckoning. A thorough and irreversible realisation that the footloose, fancy-free portion of the first 20-plus years of our lives is firmly on its way out.
Now we're entering the part where decisions can't be unmade. Where consequences are permanent. Where things matter and the people you choose - and create! - are your responsibilities forever. And this part is the entire REST OF YOUR LIFE that requires - no, demands - a new level of love and emotional resilience.
And that's the best-case scenario. I'm not even going to broach the whole thing about the constant and inescapable drum of anxiety regarding the safety and well-being of your loved ones.
I should end with some sort of uplifting take-away. But I really don't have anything else to say except that it's terrifying and I'm already exhausted.