One of the most detrimental pieces of advice to empaths is to be less empathetic.
When you're suffering in service to others, you don't 'tone down' your empathy for others.
You tone up empathy for yourself.
This means asking questions around the first and second spheres of empathy, to better self manage:
1) Why is this important to me? (First sphere, reconnecting to why)
2) What state am I in? Am I rested? Eaten? Calm? (Second sphere, your physical, emotional and conscious self)
My wife constantly reminds me, "you can't be a good guy if you're not around."
There are a few meditations on compassion I'll paste in the comments that help me when I'm feeling emotionally drained while in service to others.
Pass it on to those who need it, and reach out to join our community of empathy practitioners, we meet once a month.