Should concealor be darker or lighter than your complexion?

Hey lovelies,
So I went to a cosmetic store the other day to purchase some concealer and the sales lady gave me one that was darker than my complexion. I told her it was too dark and she said that concealers are supposed to be darker than your complexion as to which I told her no, concealer should be lighter by a shade. The reason for this is because if you have dark under eye circles, a shade lighter will lighten this area and if u set it with your normal powder it will not be so recognisably light. For blemishes this works the same because they are usually darker than your skin tone a  lighter skin tone and your foundation and powder will conceal them perfectly.

If you were to use a darker concealer the dark circles would look more emphasised and you would have to get a darker foundation and powder to match up and this would not look right.
So a shade lighter than your foundation is the way to go..
What are your experiences with concealer? Please share...
Be blessed
Love Wacuka