Like with other neurodivergent conditions, meeting the expectations of the 'normal world' can be exhausting for ADHD people. Regulating yourself through the eight hour work day can leave your head feeling stuffy and like it's about to burst but there's no shame in taking some time for yourself after the work day.
A lot of us will have spent our lives being told we're "lazy" and "underperforming", so it's hard to shake the feeling that we should always be doing something productive. But "productive" can mean having some downtime if it leads to greater motivation and mental clarity later on.
Of course, this isn't always possible if there are other things involved like family or other work commitments, and it's whatever works best for you. Just don't feel like every moment of your life has to be dedicated to furthering 'the bigger picture'.
Don't be afraid to watch the next episode of your new favourite show or sink another hour into whatever game has you hooked right now. Read another chapter, draw something just for fun - whatever it is that clears your brain fog.
It's important to look after yourself and relaxation is a huge part of that. Different people are wired differently; don't always hold yourself to the standards of the 'always on' crowd if it doesn't work for you.
Have a good week!