Probably more imps are given away by automatically covering an honor with an honor without pausing to think.

 

Here is a hand from this mornings tournament. Do you cover the Jh or not? Why? Making the right decision made a 13 imp difference.

 

The contract is 5d. Your partner has bid both spades and clubs. They start by cashing the K and then A of clubs - all following. They switch to the 9 of hearts, declarer playing the 10 from dummy.