It's murder to doubt yourself in life. It took until I was 45 to get to that point. As hard as it is in your work, it's harder in your life. But it can be done.
Of course we all have our limits, but how can you possibly find your boundaries unless you explore as far and as wide as you possibly can? I would rather fail in an attempt at something new and uncharted than safely succeed in a repeat of something I have done.