Honestly, whether joking or not, that might just be all you need. I've seen it go a very long way. Godspeed. Besides, being able to admit being dumb about some things probably indicates that you're much smarter than many who can't.
I feel the same way about myself. I don't consider myself a smart person, but dammit I have a great work ethic and I always give 100%. It's gotten me this far, but not sure if it can take my all the way to a PhD.