Today's necklace* is a spiral. It curves to the right, symbolizing the virtuous spiral. A simple example of a virtuous spiral is a rich person. Since he has so much money, he can save more money and invest more money, which gives him more money. In this sort of spiral, things build on each other positively.
Usually, my symbol is the vicious spiral- curving to the left. An example of this is being bad at math. You are bad at math, you feel bad about it, you procrastinate on studying it, you become worse at math, you get math anxiety, making you perform worse on tests and so on and so on.
Due to my negative bias, I believe the latter is most common. A related term is'virtuous circle', which refers to pretty much the same thing as the spiral, I just like spirals better than circles.
* I wish that I had such a nice necklace. My spiral is so plain.