Always start slow and do not be too ambitious. I know it is very difficult to hold yourself specially if you took the time and effort to go to the Gym and want the best outcome from the time you spent or spared for this event.
Total 45 min **at the beginning **as you mentioned is a bit too much.
Always start cardio on short time like 5 to 10 min. if never was done before or was not done for a while.
Never drink water in the middle of workout.
Never drink water immediately after work out.
It is okay to drink water or mineral fluid about 30 min or more before work out though.
I do not think you will die of dehydration immediately after exercise unless you have some other medical issues.
Always take a break between activities which involve extreme exercise activities.
Print this and put it on your refrigerator with a magnet for future reference. …