I know it'll be obvious things like rapid heart rate or lifestyle restrictions.... but for me, at the moment at least, it's excessive sweating?
Being back at work, it's a half mile walk on the flat.... and even if I walk slowly and am not wrapped up in a fleece plus workwear I'm drenched when I get there. Hospitals are a warm place anyway but some days even sitting still I'm clammy.
Walking to school (half a mile there half a mile back), even when there's dew on the cars and a breeze in the air, I get back with my clothes sticking to me no matter what I wear!
It's starting to get annoying.