Applying a nice elongated cat eye shape on the eye shadow is a detail that many find difficult. It can be tricky to know exactly how far from the eye and in what slope you should put on make-up so that it will lift the gaze in a natural way.
A tip is to first apply the eyeshadow in the outer corner of the eye, and fade it out as wide as you want the eyeshadow there. Then you can imagine a straight line from the nostril and obliquely upwards past the eye shadow that you just applied. In that slope, you can make your cat eye shape to get it adapted to your own facial features! :) In addition, it is easier to get both sides the same if you have a concrete slope to follow.
If you have difficulty seeing the lines in front of you, you can use your make-up brush as a guide!
Hope you understand what I mean and that this tip was helpful!