I think it just takes practice, practice, practice, practice, practice.
The more you do it the easier it becomes. Just think to keep changing directions. Slowly and a slight curve, but go in different directions. I find it harder to do a big stipple and easy to do little ones. I like to do curls and heart shape leaves.. Kind of a vine effect. then you are allowed to cross lines... A glass of wine would help, just relax and go.