It wouldn't hurt you to be a bit more serious.
Wouldn't/won't/never hurts make perfect sense in this example. I'm wondering if there's any alternative way to preserve the meaning of this phrase in a little bit less strict context, while also avoiding a negative connotation, such as in these sentences.
- It (or whatever) ... to say "Thank you".
- It (or whatever) ... to keep an eye out for the perfect job.
And if there are other ways to say never hurts, what do you think about their differences then?