Late last year, I spoke with a friend about climbing mountains and running marathons. A parallel was drawn with The Human, Earth Project - in a sense, the Project has been a way of testing myself, and discovering where my limits lie.
How far was I willing to go before I turned back? At what point would I decide it was too difficult, or too dangerous?
The previous summer, I'd faced a similar quandary amongst the peaks of the Canadian Rockies. I'd set out with two friends to climb a particular mountain, and we'd summited earlier than expected.
From the top, we could see a larger peak looming above and beyond the one we'd climbed. The three of us decided to continue along the ridge and attempt the second peak.
Some hours later, as we approached the second summit, we lost any hint of a trail amongst the scree fallen from the crumbling cliffs that surrounded us. We turned one way and another, hoping to stumble upon any kind of path to lead us to the top, but that path failed to materialise.
At a certain point, we realised there was no longer enough time to safely negotiate the rocky summit. It was a real letdown to come so close only to turn back without bagging the peak, but we did.
It was a difficult decision to make, and we delayed it as long as possible, but it was the right thing to do. For the sake of a few metres, we never reached the top of that mountain.
The fact that we'd reached much greater heights than we'd ever intended no longer mattered to us - yet it's our defeats and disappointments that give meaning to our victories.
In May this year, against all odds, I succeeded in locating and meeting with my friend M who had been abducted from Vietnam and trafficked to China, where she had been sold as a wife to a local man.
It was incredible to have reached such heights - but beyond that peak lay another more perilous.
For more than a year, I'd been working together with Blue Dragon, a Hanoi-based NGO that rescues girls who have been abducted from Vietnam and sold as wives or prostitutes in China.
Having acquired M's phone number, determined her location, and confirmed her wish to return to her home and family in Vietnam, I believed it would be a simple matter of passing that information to Blue Dragon, who could then arrange her rescue.
The cavalry had been called, and I could step away. My job was done - wasn't it?
Some summits can seem deceptively close, only to reveal themselves to the climber as a series of false peaks.
The political situation had soured, Blue Dragon's hands were tied, and there was no way of knowing what would happen to M if the Chinese authorities were alerted to the matter. M was unable to escape by herself, and needed help.
Who else was there?
M herself had chosen the timing of her rescue - immediately after her baby girl's first birthday in the first week of August. With the constant risk that she might fall pregnant again, something had to be done quickly.
I'd already come much further than I'd ever imagined possible. I'd gone beyond what was to be the end of The Human, Earth Project, and found myself in uncharted territory.
I booked my flight back to Hong Kong for the first week of August.
In the weeks leading up to her arranged rescue, I'd spoken less frequently with M. I was cautious not to arouse the suspicions of M's "husband", the Chinese man to whom she had been sold.
In any case, communication had become more difficult with the poor-quality Internet connections I found in Nepal and India. Having left China I could no longer contact M from a phone of my own, nor could I add credit to her account so that she could reliably receive my calls.
In early August, after having lost contact for several weeks, I needed to confirm that M was ready to leave. Repeated attempts to call her had failed, and I was finally able to speak to her only 48 hours before my flight.
A rescue was impossible, M told me: her "husband" and his family were watching her too closely. She was being kept essentially as a prisoner in the house, and was unable to have more than a few moments unaccompanied outside.
There was no way she could rendezvous with me, she said, and asked me to wait another six months. I asked her why six months.
In six months, her "husband" had told her he'd be sending her away to another city for work.
Alarm bells were ringing.
M's Chinese "husband" had purchased a trafficked girl, made her his wife, and was using her to continue his line. He was aware that a friend she'd known from her former life in Vietnam had now contacted, located and met with her.
I'd even met with M's "husband", if briefly, and somewhat accidentally, and felt an enormous personal responsibility for my role in the matter. M had assured me it was safe to call and to meet her - but was she herself aware of the risks she was running?
M had become very complacent in her current position, and prided herself on using what little power she had to make life difficult for her "husband". With her spirits soaring in anticipation of her return home to Vietnam, she'd become cocky, and was terrible at keeping secrets.
M's "husband" didn't need to suspect her plans to escape - she admitted to having brazenly flaunted her intent to return to Vietnam in the course of an argument.
Now she was a prisoner in his home, and he was planning to send her away.
Where was he sending her, and for what kind of work? I asked. Why six months?
M didn't know, and didn't much care. She celebrated the news as a possibility for greater freedom from her "husband". To me, it was the absolute worst news of all, a danger far worse than a second pregnancy.
Her "husband" had now been alerted to her hopes of freedom, and had far more at stake than the wife he'd purchased. If caught with a trafficked bride, he was likely to face a lengthy prison sentence.
Given the facts, it was highly probable that M's "husband" was trying to wash his hands of her. With the great demand for women in China, not only would he rid himself of a dangerous liability, but he would also be able to benefit by her sale. Was he already looking for a buyer?
I'd spent five months trying to find M. If I lost M's location and phone number, all of my work would be undone - and M herself had much more to lose than that.
M was now damaged goods. If she was to be resold, there was a very real chance it would not be for marriage, but as meat for the brothels - and she was blissfully unaware.
I spoke to Blue Dragon, who seconded my suspicions. I had to find a way to get M away from her "husband" as soon as possible, however difficult it might be.
I called M to tell her so, and a male voice answered the phone. I hung up.
I called again the next day, at a different hour, when M was generally alone in the house. Again, it was a male voice on the other end of the line.
It was too risky. Her "husband" knew too much, and it had become dangerous to even try to speak to M.
How much of this was my fault?
Six months, she'd said. Why six months? Was he waiting for her child to grow stronger?
Perhaps I was wrong. Perhaps M's "husband" hadn't yet made the decision to sell her. If I stopped calling, and M made no move to escape, perhaps his suspicions would subside.
The summit was in sight, but out of reach. What was I to do? Whichever way I turned, I'd be exposing M to danger.
Two terrible options lay before me, and the decision I made was even worse. This time, I should have pushed on to the top, whatever the cost - but I didn't.
I cancelled my flight, and stopped calling. I chose to wait - knowing, with every day that passed, that anything could happen to M.
It gets cold up here in the mountains.