Recently, I had a discussion with some postdocs about how to communicate about leaving academia to possible future employers.
In the end, I believe it is not a question of why you want to leave science; It is rather the question why you want to have a specific job outside academia: what motivates you to apply for this job and why do you think that you would be successful in this job – and that’s what future employers are interested.
So ask yourself the questions which skills and interests are distinguishing you from others. In performing which kind of activities have you proven these skills? How will they enable you to do the new job?
In her article on CAREEREALISM.COM, Karen Siwak moreover highlights the importance of being “realistic about your qualifications” and not to “apply for jobs for which you are clearly unsuitable” for reducing tension in the recruitment process.
You will feel much more self-confident, if you are clear about how your skills fit to a specific job. Possible employers want to be convinced of your motivation and your fit to a job. You can only convince them, if you are convinced yourself!