I've never thought of myself as being particularly "gritty" in anything; for me personally, mediocrity is good enough. I'm boring in that I get up and go to bed at reasonable times, in that I play video games for a couple hours at most, then I think I've had enough. I'm not trying to humblebrag, it's not something I do conscientiously, my main point here is that not excelling, not "doing your best" is also fine.

In agile methodologies the phrase "sustainable pace" is a recurring theme. You'll be in this life for 80 years if you're lucky, no need to burn through all that in a few years.

I've worked for nearly ten years at my previous company (consultancy), the most dedicated, hardworking people all ended up with burnout. I mean sure, I guess they earned a bit more money and stuff, but they also spent at least six months up to a year completely out of action, some went straight back into it and had to be put out of action again. And I hope they ask themselves "was it worth it".