Okay so yesterday I decided I was going to jog 2 miles. Well I drank some water and started my jog and made it about a half mile then decided to walk for a few seconds. Then I started back jogging. I live in north GA and its extremely humid/ hot right now, so I don't know if thats why I couldn't continuously jog. I only did about 1.5 miles and then came home. Well, when I got home I was going to finish up my cardio with a few pushups, situps, and pullups. I did all of that and then drank some more water and laid on the couch for a while. When I got up off the couch everything started to go black and I got dizzy so I tried to get back to the couch to sit down but I tripped over the table and fell down. It took a while for my sight to come back. Why did this happen?