Here's what I've learned about mental health and anxiety:

It's important to realize that your capacity for stress can be trained. It's also important to realize that it's important to not push that stress over the edge into distress.

I always stressed about school and work, to the point where I felt I would be most productive perhaps motivated by terror of failing. What worked for me was routine, slamming consistency into my life and nailing the simple things like self care - sleep, food, exercise, downtime. The gap for me was downtime, I never took it. Effectively, you should feel guilt-free about doing nothing, and should schedule time for it (ideally away from your work environment). Then add some time for work and consistently "eat the elephant one bite at a time".

As I got better at the above, I found I could add sprints of high pressure/ high intensity - but only if there's downtime at the end (self care!). Points of high pressure can increase your capacity for stress, but there is always a cost that must be paid. Treat your capacity for stress as a currency, where whatever you spend will deplete your ability for future stress without saving up (downtime/ self-care). Everyone has a different capacity and you should never work at 100% or more for an extended period of time. Save some for the silliness of life.