Have a shutdown routine at the end of the work day and ensure you are not thinking/doing work after those hours are done.
Reasons
Limited time/capacity for deep work during the day anyway
As humans we are not able to squeeze out intense focused work for multiple periods of time at once, like 4 hours at max. The more you cultivate this practice though, the more you are able to sustain it.
If you do the work task in the evening, it is likely not your best deep work anyways, so better preserve those prime hours earlier in the day.
Leisure is good for the brain
It restores your energy, and also, your unconscious is also able to tackle problems on its own in those moments of rest.
We can think of the concious mind as useful for directed constrained tasks, like math, and the unconscious - for choices that are more fuzzy and require broader creative thinking.
Professionals take rest seriously.
Zeigarnik effect
The unconscious mind worries about incomplete tasks.
By having a clear stop to your work day, you ensure your mind is not thinking about the remaining things to be done.
A good suggestion is, at the end of the day, to review the tasks you’ve done and the incompleted ones. Make sure each item has a plan or is captured in a system you trust. Additionally, Newport says the phrase “Shutdown complete” to emphasize the end and provide psychological closure.