Another anecdote is that sometimes "just power through" is a trigger phrase that leads down a path of shame and self-criticism which only serve to fuel deeper depression/anxiety/stress and so forth. There's a cultural myth that people who struggle are weak and less than people who are successful. Depression can really amplify that story. When I'm in that place I need to scale back expectations, find something (anything) I can do that's healthy, and cut myself some slack. The truth is we all struggle and success has many dimensions.
The "just power through" line isn't wrong, in fact, it's exactly what I need to hear sometimes. But it can also be exactly the wrong thing. I think it needs a heavy dose of empathy and compassion along with it.
I powered through writing my dissertation and got a PhD.
I powered through a workout that felt wrong and got rhabdomyolysis.
You win some, you lose some. Consider the risks and the rewards.
Anecdote:
When I depressed or stressed, taking action and following a preset list of tasks (brush teeth, hit the gym, make lunch) doesn't 'cure' my mood, but it does reduce my anxiety/stress/depression.
By "powering through it" I stop stress driven by inaction (e.g. not brushing my teeth while result even more stress later).
If I stick with my routine, it reduces my cognitive load, allowing my brain time to calm down. Its similar to how mediation helps you stay calm. Following the routine reduces the number of decisions I need to make.
As much as I might want, taking a sick day to lay in bed all day doesn't help anything and would make me more depressed as I think about all of the stuff I should of done.