What do you need before you can have your mirror image?

You need your self.

But, if you need yourself before you can get the mirror image, then what is there before the mirror image is not the mirror image.

It is not different from the mirror image either, but the whole experience can be divided into that which occurs during the experience and that which preceded it.

Most importantly that which precedes it, is not what is in the reflection. It is what is needed in order to see that reflection.

The whole mistake of ego is to secretly replace what was there before, with what occurs within and after: putting the cart before the horse. So doing the cart comes to think it is pushing the horse. Welcome to exactly the experience of embodied ego which thinks it has the power, control and choice to do things and think things. All this is in the reflection! The horse and the power is elsewhere!