For the past several days I have been thinking about the question "what is the function of his anxiety ? It does not seem to be based on any realistic appraisal of his abilities."
Traditionally, Cognitive Therapy tends to look at anxiety (and other affect) more as a result of cognitive processes than as something which has a function of its own. Our traditional answer would be that Jessica has it exactly right. The anxiety which afflicts Gary is not based on a realistic appraisal of his abilities, it is based on an unrealistic appraisal of his abilities. Gary saw himself as an incompetent who had barely gotten by with the help of his sisters (and later his girlfriend). He feared that at any moment his incompetence might be revealed.
While this view of Gary's anxiety makes sense, I think it makes sense to also think in terms of the function, not of Garys anxiety, but of his worry. In his anxious vigilance for possible problems and his rumination about them, Gary was engaged in a misguided attempt to forestall disaster. While it seemed clear to me that he experienced considerable needless anxiety and encountered many problems that were a result of his vigilance and worry, Gary assumed that his vigilance and worry resulted in his avoiding even greater problems.
This is an important point because as long as Gary believes that his worry prevents disaster, he will be unwilling to abandon it even if we are able to find effective ways to eliminate his worry. At some point, I will need to help him discover that the worry is both dysfunctional and unnecessary. Otherwise he will resist any attempts to get him to abandon his worry. I also may have to help him learn some way to approach potential problems without worry. Afterall, he has been worrying vigorously for many years and he may not know other ways to approach challenging situations.