That's the thing, communicating stuff before you become upset. For example, my SO used to come from work exausted and used to lie down in the sofa, slept until night, then maybe grabbed some dinner or just slept straight until the next morning. Sometimes we didn't speak at all in 2 to 3 days because they woke up earlier than me, they then went to work in a hurry, no talking in work because work takes 200% of focus, and then come back home to their date with the sofa, and end up sleeping again before I finish my work.

Now we chat about our day at lunch even if we are not together and they vent about it whenever they can so that when they come back, I can make some time for them, and they also manage work stress way better than before so they don't come back utterly exhausted every day. Learning that they could not work in the field they were working and live to tell the tale and taking the time to change fields with my support helped a lot too. The situation mentioned above was before they were diagnosed and they just bruteforced the workday in a super toxic way for them and those around them (me).