If you’d like to opt out of being notified when your client completes a field, head over to Settings, which can be accessed by clicking on your avatar within the top bar.
From there, select Personal.

If you scroll to the bottom of your Personal Settings, you’ll see the following:

This area will allow you to disable field notifications completely by ensuring that the first option has been slid over to grey, like in the above.
Alternatively, by enabling the notification limiter and the field completion emails, you’ll receive just one email daily, cutting the volume by a great deal.