Apply Self Regulation and Accept Feedback

The earth has a balance point. Natural systems that at first glance seem healthy and vibrant are often suddenly stricken with an infestation of pests or diseases that have a changing effect on the plants and animals in the area. Typically the initial damage seems shocking and unfair, but after time the benefits of this check start to show. This is natures' way of self regulation. Often the feedback is not realized for sometime before and after the event, then a flurry of regeneration explodes to life.
Apply Self Regulation and Accept Feedback
The fourth principle is a deep one. Sometimes it can be very traumatic to the system or the people it involves, but everything will work out for the better after time.
Everybody has heard the phrase "too much of a good thing." This principle is the counter measure to that phrase. We want to place limits on our inputs and outputs. I will give you a couple of examples.
Chickens on pasture are fantastic. They aerate and boost soil fertility, control pests, make fine companions and produce a tremendous yield. Indeed one of the best additions to a permaculture design is chickens. However...
Chickens will destroy a landscape if improperly managed. They will bare the soil, over fertilize, attract unwanted pests and predators and cause conflict between you and your neighbors, or worse the department of making you sad.
We must apply limits, or set boundaries where the birds can be day to day and we need to accept the feedback of how the system responds to this management.
Another case of too much of a good thing can be money. I know, I know, I am not arguing the value of money as a barter item or whatever.  There is a place for currency, and there is indeed an implied necessity for most people on the planet to possess some kind of monetary yield.
Money, in the wrong hands can be terribly destructive.  The power of money can cause decent folk to do wrong and undecent folk to be martyrs. Even on a smaller scale it can be dangerous. What if you bought every plant in your design, never planting a single seed or grafting a single limb. What if you hired out for every project in your design? I would say you would be selling yourself short. You may have a beautiful, productive landscape but you would competely lack any spiritual connection to it. You have to remember energy always flows back to its original source. A little financial pinch can make you a much more productive human being.
Properly checked a permaculture system can be a robust ecosystem and you will avoid many problems that can and will arise out of the abundance.