I was reminded today of an observation I made a while ago: any commitment means making sacrifices. It's very easy to say "I'm going to get this project done no matter what", but the reality of what that means is actually pretty extreme. That "no matter what" means you would be willing to sacrifice not only other projects but friends, family, sleep, even happiness entirely to get it done. But when the chips are down most people aren't willing to sacrifice that much, and probably for good reason. Usually we either don't really mean the commitment, or don't consider that sacrifice involved.
This lack of realisation also happens in much less extreme examples. Something like "I'm going to exercise every day so it becomes a habit" is a popular and often abandoned commitment, because people don't really think through the consequences. It's not just exercising, it's sacrificing the ability to not exercise – not exercise when you're tired, not exercise when you're busy, not exercise when you feel sick, not exercise when there's something way better and more fun to be doing. It often breaks down because the commitment you made didn't reflect your actual priorities and, confronted with an actual test, those priorities won.
Given that fragility, I think there's a lot of benefit in being more explicit about priorities and sacrifices. If there's something you want to get done, or some commitment you're considering taking on, better to play it off against the other priorities in your head before you commit to it. Where does it really stand? There's nothing wrong with "I'm going to exercise every day unless I have a work thing on or I'm tired", but it is a different commitment. Maybe a less impressive one, maybe one less likely to form a habit, but also a more honest one.
And, really, a dishonest commitment was only ever going to deceive you up until the point where you had to sacrifice for it anyway.