This is the most effective way to use a mirror while grooming.
1• Spot the place you want to groom visually in the mirror.
2• Place your nail exactly on it.
3• Move away from the mirror.
4• Groom your skin.

Proper grooming is performed using sensations emanating:
• from the skin that is being groomed and,
• from your nail and fingertip, as they manipulate the skin.
Those are very faint sensory signals, and you must dedicate your full attention to them if you want to decode them.

As soon as you use your sense of sight, it takes precedence in relaying information to your brain.
Even when you are grooming correctly, and relying on tactile data, the simple fact of taking a look at your hand shifts your perception back to visual immediately.
So, you can't look at yourself while grooming, even when no mirror is around.

Don't use a mirror for more than 5% of your grooming activities.
Relying on a mirror while grooming is an easy habit to take, so I warn you against it.
Stay away from the mirror while grooming.

If you use a mirror more than 5% of the time; your grooming will be improperly done.
Your technique will be biased, and your work won't succeed.
You may be convinced you're doing things correctly, but your movements aren't guided by the right sensory input.
You must rely on your sense of touch; on signals from your nails and fingertips, as well as the skin you're grooming.
Your visual perception is so powerful that it overrides your subtle sense of touch.

On the other hand, that 5% of your grooming time spent in front of the mirror is important.
You can visually spot problems that you hadn't noticed with your nails.
You can gauge the progress of your grooming efforts.

While grooming, it's easy to get lost on your own skin, because you don't see.
Your hands move all over, and you lose track of where you are.
You confuse the left with the right, the top with the bottom.
So;
• Occasionally checking your position with a mirror is instructional.
• You can make the link between what you feel and what you see.