Just read Hol's post. Yeah - we all feel like that sometimes - sometimes it becomes a lot of the time.
Identifying with a job is what breaks old people apart when they retire and find they don't know who or what they are anymore. It is a road to pain. However, identifying with personal growth is a path that is endless, even if the activities might change. We can all be a bit better physically, but as we age, the return on the effort diminishes fast, so we could then turn more time and attention toward something else. Ultimately, we all end up identifying with something, so we may as well try to make it something worthwhile to us.