The slight dread of knowing you’re going to run out of water is a tough way to start a ride.  But, as long as you ration correctly, and don’t build up some weird anxiety about it, you’ll get through it
.  In the past 5 months, I have done this more times than I think are acceptable, but each time I’ve learned a good lesson about mental fortitude and physical limits. 

At least it was a nice day!

Still being able to push at 70-80% for the whole ride while taking in too little water is an interesting and unique challenge each time you do it, because the external factors like the weather, and the trail being ridden are not consistent.  You must “feel” it out as you go, deciding at what intervals you ought to drink, and for how long you can possibly wait to indulge in a sip. 
What makes it more interesting, is when the whole group is poorly prepared and everyone is dealing with the same questions regarding effort/rationing.  Thankfully, this wasn’t some crazy survival scenario, it was just a fun, albeit poorly planned for, Saturday ride with friends.  But the lesson each time never changes: be better equipped for the journey ahead, but don’t underestimate your ability to push yourself physically and mentally.