The healthy answer lies somewhere in the middle.

Burning out trying to overdeliver and prove your worth is no better than underdelivering and slacking off.

There is a balance. Exceeding your employer's expectations is of course a good thing as a salaried employee. That's how you build a highly successful career.

But one of my expectations as a manager is that you manage yourself so you're still around 3-5 years from now and don't need to take a break for mental health reasons.