Having worked for the past 25 years in high- and low-stress jobs the consistently most important thing to make sure you are effective at work and still have your mental health is to prioritize your time and work at least every morning. This prioritization should be shared with your boss (at a high level, not every task) and you should give them an opportunity to help you reprioritize. Most people can work a 40 hour week and have an impact in their job if they consistently do the things that are most important to their employer, and aligned to their skillset.