Suppose someone asked you to think about yellow canaries. You'd conjure up all sorts of yellow canaries. Your mind would be filled with yellow canaries, possibly socializing with Tweety. These yellow canaries would be keeping a sharp look out for Sylvester, too. Pink elephants and yellow canaries don't have much to do with skydiving, but the idea of thinking or not thinking about certain things does.
Nervous jumpers are usually easy to spot.
The very last thing they want, is to be identified as a nervous jumper. Their reaction will be to concentrate on covering up their nervousness. Emphasizing nervousness will not enhance any skydive. A better plan is to concentrate on the positive aspects of the dive. Talk about the great view from the plane, fresh air at altitude, fantastic feeling of freefall, sense of accomplishment and other such things.