Hi, I’m new here, prompted to join to ask about a recent qigong  practice where, at the end of 2 hours, suddenly I felt like I would pass out - dizzy, nauseous, ears ringing like crazy. 

I’m getting back into qigong after a long break. Started in my new town with a new teacher who seems quite competent, having tried a few others. Had excellent teachers in the past in China and in the UK. 

It was a good and challenging practice. 90 min in I felt a bit dizzy (highly unusual for me), took a short break for water, and felt fine to continue. Then at the very end (30 min later), suddenly I felt like I was going to hit the floor, literally.
 
Today I feel great but am left wondering… What was it that happened yesterday? I’d had food 2 hrs before practice, knees weren’t locked, was well hydrated, etc so no obvious explanation.

Thank you in advance for any thoughts or suggestions for practice to prevent the sickness feelings arising again.

I think it's quite a personal thing.

Sometimes I've pushed too hard and hit a wall towards the end of a session. If I bring some anger/tension from my day into the hall that can be draining.

Sometimes with a new teacher the energetics of the room has been unfamiliar - Zhi Zhing Wang (sp?) many years ago and my local taijiwuxigong teacher have both affected me in ways I wouldn't have expected from the simple exercises I was doing.

Best
Rich

I suggest you to ask the question on this forum too:

https://www.thedaobums.com/forum/179-daoist-discussion/

metta

Thanks for the suggestion, Nicolas. Will do.