I have been diagnosed with an anxiety disorder and I feel the same way about it. It's not an illness, it's simply a maladaptation to the kind of world we live in.

Most milder mental disorders are probably like this; it doesn't make any sense from the evolutionary point of view that a significant proportion of the population would have largely genetic trait that is only harmful in all situations. It's just that traits like ADHD and high levels of anxiety probably were helpful - or at least not harmful - in our evolutionary context, but are not anymore.