Working hard gives me wrinkles.

I love making these little cases with "work hard and smile" on them and think it's a pretty good motto most of the time, but the other day I was looking at these thinking, "who smiles when they work hard"??!! When I work and/or think hard I get this really serious face on which causes a deep wrinkle across my forehead and I'm pretty sure it's gonna permanent soon. I catch myself with "serious face" all the time and have to snap myself out of it.
Maybe I should try and smile while I work hard, it would relax my face, therefore not causing permanent wrinkle. But I would look like a freak,  and I think it might be impossible to work/think really hard AND smile at the same time.