Good and bad so far

So I've started on my gym instructor course recently and most of it seems pretty reasonable so far but that's from many years of gym experience helping me I think. Today however was one of the weirdest days though as I am excited to be starting a new chapter of my life as I'm on the road to becoming a instructor which to me is one of my dream jobs but today's gym session wasn't the best. So I went in after a weeks break and decided to do a whole/full body workout, did my bench press, squats but then went I started my seated rows I suddenly became overheated and was fearful that I was about to pass out. As you can imagine this wasn't much fun and hasn't happened to me before so hopefully next time I go in 2 days time I will be back to normal. I'm just happy I knew to stop right then instead of forcing myself to carry on as who knows what may have happened if I passed out doing an exercise so its rest for me and a bit of course work. I think its my poor sleeping habit which I got into after Christmas so that's my priority at the moment to sort out and then see what happens over the weekend.