After several years of use, you may experience some leakage through the fabric. You may apply a water-repellent compound on your tent fabric. This will temporarily improve fabric leakage. However, this compound may eventually deteriorate the fabric, and may increase the possibility of suffocation. Check to make sure the compounds you purchase are free from this risk.
People exhale a tremendous amount of air while sleeping.
This gathers at the top of your tent and becomes water droplets due to temperature differences between the inside and outside of your tent. To improve this situation, ventilate your tent. This can be easily accomplished by opening the door and windows slightly to allow the temperatures to balance. If you find the zipper open somewhere in the middle, pull the zipper slider all the way down and slide it up to the other end slowly. This will repair your zipper.