6:11 of this youtube video does a great explanation of how calling out which ball is being thrown can help.

While I found it did help me a small amount, I still have a long ways to go if I want to be a fluent juggler.

Here’s how it went

Some of the key things I need to focus on is not getting frustrated, throw the balls closer to my body, and find a good rhythm, get all the balls to the same height, focus on each ball at the top.