Most people have one or two things that they do which are well engrained, well practiced activities that they enjoy and can really start challenging themselves on. But for a lot of people the big challenge is establishing those activities in the first place. And with those I've found that the idea of establishing a non-negotiable performance threshold is a bad idea. That kind of all-or-nothing thinking leads more often to nothing than to all. It's basically why so many new years resolutions fail.
The new years resolution problem is an interesting one. A lot of people treat failed new years resolutions as a pseudo-moral problem, insisting that failed resolutions are due to a lack of desire, or discipline, or passion for whatever good habit is in question. But moral language like that isn't really good for solving the habit problem. It's a motivator (and a good one!) but not a great diagnostic tool, because all it does is generate a bit more motivation by harnessing emotions like meaning, and aspiration, and guilt, and shame.
If you view it from something more like an engineering perspective - i.e. how do I set this whole thing up at the start so that less people fail - one of the best strategies I've found by a wide margin is to set the "non-negotiable" threshold as low as possible. For people looking to build a swimming habit, for example, the single best thing they could do would be to commit to being in the water every day without fail, and then to do the work that seems appropriate for that day.
Once it's become a part of their lives, for probably a year or so, and they've had many days where they've pushed their boundaries already, then they can set the non negotiable bar higher.
The reason I'm bringing this up here isn't because I disagree with you. I actually think your point here is great. But for a lot of people the first and most difficult threshold to cross is fitting a new, healthy habit into a chaotic life in the first place. That's the first thing that needs to be made non negotiable, and I know it works because in my own life the type of self-imposed performance target you're suggesting here was something I tried and failed at many times. It wasn't a problem with character or passion - it was a fundamental misunderstanding of what it took to develop a discipline in the first place. Since then I've used the gentle approach to transform myself into a disciplined writer and worker, and recently, to start transforming my health as well (got a ways to go on that front).
So the only thing I'd suggest as an alteration to what you've said here is that for those who already have a path forward that they are familiar with, the best way to supercharge life is to start setting a performance target that you refuse to miss. But for those who don't-- for those who aren't daily swimmers, so to speak, or who don't have a history of it, the first non negotiable line should be getting in the water.
