A lot of our sense of being comes from the work that we do. It's completely normal to define yourself, as an individual, through your occupation. It doesn't matter if you're an accountant, teacher, writer, doctor or even a stay-at-home mother - your work is usually part of your central life.
Before you retire, make sure that you are secure with your identity. There may be a way for you to still partake in your occupation as a hobby. For example if you're a writer - it may be wise to start a blog, a book or even as simple as writing your thoughts in a journal. If you're a doctor - continue to research areas of interest and submit writings to a journal. There are a limitless amount of ways to keep your identity intact.