Dr Surenthiran says "don't overdo it on the good days"
you need to rest, while keeping some moderate activity.
i have the same issue. i was feeling great yesterday, went to the local outdoor pool with the kids, was swimming in the sunshine and then started getting migrainous eye symptoms - no doubt set off by the flashing/sparkling/moving sunlight on the water. yep, and today is worse, headache, brain fog and a bit of dizziness back.
i think they key is to do stuff, including exercise, but to keep it well below the level where it triggers your symptoms.
i struggle with this, on the good days i want to run, do 100 things, work, etc. but if i do too much, it sets me off and i get a bad day.
i try to think of it like a broken leg. it may feel ok in the morning but that doesn't mean you can go and do triple jump in the afternoon. it's just a bit harder to gauge with MAV because you don't have a set timeline like you would with regular physiotherapy.
rule of thumb - do a bit less than you think you can get away with. if you are ok with it, next time do a tiny bit more. but don't suddenly think you can do everything, because you might well set yourself back.
try doing exercise that will calm you rather than aggarvate the symptoms. i haven't tried yoga yet with MAV - anybody had any luck with that??