Ok, putting aside it's important to be emotionally warm towards your children and ensure they understand you love them "unconditionally"[1], I do think it's also important to help them to learn retrospect and to work smarter.
"What a great mark you've earned! What do you think was working about your approach?" (then praise and encourage them for whatever they say so long as it's remotely reasonable). I just say this because I feel like the "work hard" mentality actually hasnt served me in life. Once you work for a business no one cares how "hard" you work, if it's not smart first. Smart is the more powerful variable, you can work Smart and not hard and be quite successful. But work hard on stupid things? No one cares and you'll be overlooked and even hated on at times.
[1] - I'm not a parent, but honestly everyone has a limit, and frankly love should not be truly impossible to lose. My love will stop if they butcher my wife, burn down my house, and call me fat.