As 2012 drew to a close, I was 94kg and miserable, after a slow-but-steady decline into a classic case of blogger’s physique.

It was the inevitable result of unhealthy eating habits and an overly sedentary lifestyle, punctuated by occasional, forlorn attempts to cultivate a gym habit. I was unfit, unhappy and frequently unable to walk out of a newsagent’s without a big bag of crisps.

Cue technology. As a latest resort, in January 2013 I bought a Fitbit One activity tracker and installed its app onto my smartphone, along with MyFitnessPal to track my calories intake, and RunKeeper to track exercise.

Out with the Quavers, and in with The Quantified Self. And it worked: by the summer of 2013, I was 84kg and happy. I went to the gym two or three times a week, ate healthily, worked at a standing desk, and occasionally spent a couple of minutes in front of the bedroom mirror gawping at my newly rediscovered angularities.

Oh, and I was smug about it. Quite a few friends and colleagues complimented me on my weight loss, to which I’d blush and say that I wasn’t going to become one of those people who bang on about how apps and gadgets have revolutionised their fitness. Usually going on to bang on (a bit) about exactly this.

I was a quantified smug. And it’s pretty much at that point that things started to slide.

Fast forward to April 2014, and I weigh 94kg again. MyFitnessPal and RunKeeper are gathering digital dust on my homescreen, and while the Fitbit One is still tracking my steps diligently, its app is equally unloved.

The salads and cereals are once again jostling with crisps, chocolate, late-night pasties, wine and cider in my diet. The standing desk is still standing, but some days I take my computer off it because I feel a bit of a fraud using it.

I don’t look in the mirror much, but occasionally one of my sons cackles to the other about “Daddy hatching a baby”, which is certainly a new spin on motivational encouragement.

I now feel like a quantified mug. But is this a case of the human letting down the technology, or the technology letting down the human?

The answer is a bit of both: tracking numbers can get you so far, but in the longer term, they can only work hand-in-hand with the human doing the tracking. What I’ve learned, belatedly, is that apps and gadgets are not what made me get fit.

Instead, they were important, motivating tools to track my progress on the way up to a healthier place, but didn’t help much as I slid down the other side. There are lessons here for the next generation of fitness tech products.

Lesson one, which is a personal one: for me, unhealthy eating and drinking is about stress. Like many freelance journalists, I tend to slip into a cycle of taking on too much work (which brings stress about the workload) then swinging back to a period of … less work (less stressful initially, but usually culminating in money-worry headaches).

On a bad day with an overflowing inbox and a forgotten deadline or two, I’m just a few steps from my kitchen. I’ll often find myself there absent-mindedly chomping down whatever food comes to hand, as a short-term cure for the tight knot of tension in my stomach. It just happens, usually – often I don’t even notice myself taking those few steps.

Drink? Too much sugary tea (and if I’m out, Coca-Cola) in the daytime, and wine or cider in the evenings: not quite in liver-bothering quantities, but certainly at middle-thickening levels.

The first six months of 2013 coincided with a less-work period – thus generally positive thoughts about healthy eating and exercise, as well as time free for the latter. Come summer, as money fear led to more work (and stress), crisps, cider and chips made a triumphant, belching return to my diet.

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None of this is a big surprise. Man starts getting fit in January, enjoys initial success then falls clunkingly off the wagon? It’s hardly an unknown phenomenon. Apps can’t cure stress or stop you taking on too much work. Again, not a shock. Cider remains God's own drink. But noting that it lets the devil loose on your waistline is no revelation.

My experience – and desperately hopeful that I’m not alone – is a reminder that the current generation of fitness tech is just a step in the right direction.

A lot of us are doing it: use of sports, health and fitness apps grew by 49% on iOS and Android in 2013, according to mobile analytics firm Flurry. A recent study by research company Kantar Media claimed 25% of smartphone owners are using their device to track their health, diet or exercise.

Another research firm, NPD Group, claims that the “digital fitness” category was worth more than $330m in 2013. Yet – I knew it wasn’t just me – a survey in 2013 by Euromonitor found that while 25% of respondents had downloaded a fitness app, less than 6% reported using it on a daily basis.

Fitbit, RunKeeper, MyFitnessPal and their rivals are working hard on new features, and some big players are entering the market – see speculation about Nike teaming up with Apple for the latter’s long-rumoured smart watch, and Facebook’s recent acquisition of fitness app Moves.

There is no shortage of clever tech ways to track your eating and activity. The next challenge is to apply them in ways that help you when you’re wobbling, rather than just when you’re fired up with enthusiasm.

RunKeeper has clearly been thinking about this, even if its cheery “Hey! You used to work out around this time!” style of encouragement isn’t, in my experience, super motivating when you’re nose-deep in a packet of Monster Munch.

Human willpower can’t be taken for granted, and while exercise IS a good solution to stress, that’s often forgotten by a stressed person. As a side note, too, the very device that sits at the centre of our self-quantification – the smartphone – is arguably doing the most to erode our work/life balance as a notification-barraging enabler for our willingness to be online round the clock.

The most important lesson is to resist the temptation to see technology alone as a solution for our fitness issues. It’s about humans – including the underlying lifestyle issues that contribute to unfitness and/or unhappiness in the first place – and about the humans around us providing support when we wobble. Ideally with less of the baby-hatching merriment.

This week, I went back to the gym, remembered how to enter wholemeal toast into MyFitnessPal – well, remembered wholemeal toast as a concept, if I’m honest –avoided a four-pack of Scrumpy falling into my shopping basket, and sat down to think hard about managing my workload.

Technology will still be playing a role in my efforts to get fit, but it’s not the solution. I am the solution, hopefully. But not in a smug way.

• What are your experiences with fitness-tracking technology? Share your tips for staying on the wagon, or the lessons you've learned from toppling off, in the comments section