Drop Shapes... What do they mean in magic spells?

Is it a teardrop? A sweatdrop? A raindrop? What the shape is, can make a huge difference in how it is to be read. A teardrop might indicate sadness or disappointment, whereas a sweatdrop could indicate hard work will be needed. A raindrop might suggest some disappointment or obstacles but probably to a lesser degree than a teardrop.

When we get such shapes, how are we supposed to read them as far as determining the success guarantee of our magic spells?