There's some great advice above!
I agree that this is less about grades and more about cultivating a "growth mindset" to prepare him to welcome challenges and tap into his intrinsic motivation for the long term.
There's tons of reserach about what this means, how to encourage/nurture it, and why it all matters.
Here's a short(ish) summary:
http://www.westpoint.edu/cfe/Literature/Caluori_14.pdf
For more, check out Carol Dweck's book (Mindset) -- she's a Stanford professor and has done TONS of research to inform her recommendations.
Also, Google "Habits of Mind". Our school district uses this curriculum quite a bit to encourage "growth" mindsets and strong foundational skills to support learning and achiement.
It's terrific stuff that you can weave into your conversations and approach at home. It can be really helpful to everyone (parents and kids!)