Don't be sad, just drink water. Reduced fluid intake, a.k.a. dehydration makes your heart work harder. What did your heart ever do to you? Stop being mean to it and take in at least half your bodyweight in ounces. Do you weigh 180lbs? Hello 90 ounces!! 11 glasses! 6 regular water bottles. The Great Bambino! Call it what you like.
Notice the picture on the side. Your blood is composed plasma and cellular components. Within the plasm, 91% of it is water. If there is no water in the system, your heart has to work at least double time to pump sludgy cellular components to the rest of your body.
The symptoms of being parched include fatigue...partly because your heart is working so hard. If you feel thirsty, it's too late. May as well chug a 6 pack and eat salt. If your pee is yellow, time to paint some road signs. Think about it. Our bodies can go for months without food, but only 4-6 days without water. Hmm.