Adding a second rule is where most self-directed discipline falls apart, and where real capacity starts to show.
One standing rule, held without exception, is achievable for almost anyone willing to actually try. It's the second rule that separates the men who build real capacity from the men who plateau at "pretty good, most of the time."
The failure pattern is predictable: the first rule was going fine, so a second gets added, and within a week or two, compliance on the first rule quietly starts slipping too, not from the new rule itself, but from the added cognitive load of holding two things at once. Most self-directed attempts read this as a sign to drop back to one rule, or abandon the project as too ambitious. Both responses miss what actually happened.
What happened is that the true ceiling of current capacity got found. That's not a failure. It's data. The task isn't to avoid ever finding that ceiling; it's to escalate deliberately enough that when the ceiling is found, it's found under supervision, with a plan for what happens next, rather than discovered by surprise mid-collapse with no protocol in place to respond.
This is why escalation in a structured protocol never happens on a self-directed timeline. The second rule gets added when the enforcement is already in place to catch the wobble, not before. Held loosely, two rules are worse than one. Held with real accountability behind them, two rules is where a man starts finding out what he's actually capable of holding, which is usually more than he assumed, once someone else is holding the line with him rather than leaving him to find the ceiling alone.