The Wheel of Fortune is a type of energy that stands beyond the realm of our understanding and control. Certainly you can experience its effects in life, like you feel the pull of gravity on your body. But just as you can see the apple falling but not the gravity pulling on it, so too are the works of Fate and Destiny invisible to us. Only their results can be seen, and even then, only when Destny itself decrees that the time is right for its effects to be manifested. Unlike the majority of the Major Arcana, the Wheel of Fortune hovers in the clouds, showing that you can try to reach it, but that you can never fully understand it.
The wheel is an apt symbol for the forces of Destiny and Fate because it shows how everything is connected in a cycle; some might call it the circle of life. Everything happens in cycles; we rise and fall just as a spot on the perimeter of a wheel travels from the highest point, through all the possible points on the wheel, and then back to the apex. However changes will affect you depends on where you are on the wheel. If you are at the top then any change could throw you off, but if you are the bottom then a change could start you back up to the top. And for one person to rise another must fall - everyone is connected.
Destiny seems to strike without warning, but often its effects can be seen coming if you know where and how to look for them. This is the principle of the Tarot and divinatory systems in general; to see things coming before they happen so you can prepare. Obviously if you see a wheel with the Sphinx on the top, Typhon the snake on the left, and Hermanubis on the lower right, and you know which way the wheel is turning, you can tell where each of the three figures is going - and you can also tell where they've been. Through careful extrapolation the effects of Destiny become less mysterious, and someday everyone may grasp this idea.
This cyclical structure of Fate is perhaps the only way to really understand how Fate manifests. The conclusion of a situation is found in its beginning, just as the number 10 of the Wheel of Fortune reduces to 1 by the addition of its digits. When you can realize that each beginning leads to an ending, and that each ending is both the results of one beginning and the freshly planted seed of another, then you will have grasped the essential notion of the Wheel of Fortune. And once that notion is grasped, the universe opens up to you, because you are ready to learn all its wisdom. The first hurdle has been passed and greater lessons lie ahead.
The appearance of the Wheel of Fortune shows that change is not only likely to happen, it is certain to happen, and soon. The nature of that change and the effects it has really depend on how much you understand the concepts of Fate, and whether or not you can prepare for it. Generally the change shown in the Wheel of Fortune is a dramatic change from the established order. So if you have been scraping along for a while, expect big changes in your favor within a few days. But if you've been feeling on top of the world for a long time, batten down the hatches and keep an eye out for storms - one is bound to hit you sooner or later.
No matter which way the Wheel of Fortune throws you, it's impossible to try and change it, so you might as well try to live with it. If a crisis seems inevitable, recall that in every crisis lies opportunity. When you've been swept in new direction, know that every path leads somewhere, even if you don't know where it is. When times are bad, or when times are good, always keep in mind that they won't last forever. Such events are just out of your control, and if you can accept that then the ride gets a lot easier. If you struggle against the Wheel it will crush you. So roll along with it!