To say this does not mean that this moment is a pleasurable or enjoyable one for you, necessarily. That's what we usually mean when we say things are "perfect"——that we really, really like the way things are right now. But to equate perfection with desirability is an egocentric viewpoint, not one that has big picture validity. In fact, this very moment, in its perfection, might offering me pain, or unhappiness, or some other form of discomfort. The perfection of the moment has nothing whatsoever to do with me liking the quality of that moment.
This moment is a perfect one because it is the only possible outcome resulting from the events leading up to it. The "effect" of this moment has been governed with the unavoidable logic of the "causes" preceding. If I happen to be unhappy with the moment, that doesn't spoil it's perfection, because the nature of this moment, including my feelings about it, is the logical result of things like memory, my previous life experiences, my attitude, my outlook, the current mixture of hormones and enzymes and neurotransmitters in my brain, my current physical condition, etc, etc.
In other words, dropping dead of a heart attack is a perfect result, if viewed as the logical consequence of heredity factors, poor eating habits, a dissolute living style, or a sudden contact with high voltage power lines. A truly horrific world would be the one where you don't die when a giant grand piano crashes onto your head from an overhead pulley. We need for the world to follow logical physical principles, and so it does. So how else could any moment be anything but perfect?
Viewing the world in this way——seeing each moment is a perfect one-- isn't to then suggest that we're supposed to "accept" whatever happens to us and not take action to change it. After all, perfection is also present in our resistance to the circumstances of the moment, in our choice to move in another direction.
At the same time, there's still a profound peace to be had from recognizing the perfection of the moment, even when it's unpleasant, because it then frees you from disagreeing and wrangling with the reality of it. A lot of grief we bring on ourselves isn't so much the actual pain, as our disagreement and refusal to acknowledge its truth and reality.
An interesting change begins to happen at the very instant you acknowledge the perfection of any moment. Things become exactly as they are, and immediately there is a burden that lifts from your shoulders——the burden of constantly trying to improve and perfect things. You find yourself entering into experience very directly, since there is really nothing to accomplish in a perfect moment. You just live it with a full embrace. The past is irrelevant ( it doesn 't even exist, really), and the future is interesting only because the current moment feeds it. Each moment is what it is, and the very next moment becomes an utterly logical and perfect result of the previous one. The power of our actions becomes blindingly evident, and you begin to feel a precision and economy and powerfulness in how you make choices. What you do in response to this situation is, in itself perfect, and it will lead to the inevitable (perfect) experience of the next moment. There is nothing to change, really, and nothing to regret. Only experience.
Normally, this method of seeing things comes to us in tiny little flashes, with considerably more time spent lamenting the past or worrying about the future. It is possible, though, to find yourself recognizing and embracing the inherent perfection of this moment, then the next moment, then the next moment, so that there's really nothing else but this moment, perpetually. Strangely, it's a form of immortality. String a thousand of these moments together, and it becomes a 15-second experience that can change everything and rewire your circuits in a major way.
This kind of approach to phenomenology may seem pretty esoteric and exotic, but in reality you can find it in the mystical traditions of almost every major world religion. In Christianity, for example, you will find such a practice inherent in "The Cloud of Unknowing," a seminal work of Western Christian theology.
I began to learn about it through the study of Dzogchen, a branch of Tibetan Buddhist practice, that is also known as "The Great Perfection." Depending on your leanings, you could look to either source for more information on this way of viewing the world.