Have you ever watched the behavior of horses in a herd? Horses are flight animals and their herd hierarchy is based on assignment of tasks, specifically the task of standing guard. When a group of horses is napping or sleeping, there is always a man (or mare!) on guard. The job of that horse is to watch for danger and alert the rest of the herd when that danger is present so they can get up and flee as is their nature to do. That guard horse will remain standing while the others lay down and sleep. If the entire herd were to lay down and sleep at the same time, they would be more susceptible to attack because no one would have seen it coming. This is why the job of guard horse exists, and duties are rotated so everyone gets their chance to rest.
We should take a lesson from horses when it comes to survival. Granted, domesticated horses do not face quite the same threats as they used to, but they still practice the deeply ingrained behaviors that have kept them alive for centuries. We should observe that and do the same. If you are bugging out with a group, it is unsafe and unwise for all of you to rack out together for the night. Someone needs to be on alert, listening for approaching threats and watching for abnormalities. Someone needs to be the guard horse.
Sleeping in shifts will enable everyone to get rest while still maintaining a watch over your colony. Ideally, if you have enough people, having two pull a watch shift together is best so those people can keep one another awake. A sleeping watchman is no watchman at all and can put everyone in grave danger. Keep your shifts short, lasting a couple hours, so no one is left struggling to get through an entire night without falling asleep. Also have an alert system in place, preferably a quiet one. You do not want your lookout to start screaming when they spy trouble coming. It is far better if they wake the rest of the group quickly but quietly so the looming threat can be caught off guard; put the threat on the defensive instead of your own team.
You must also consider what you will do if you are alone and have no option for a watchman. If left to your own devices, you need to have more than a few things up your sleeve to survive. You must rest to be at your best, but how? To decrease vulnerability, you need to be hidden from plain sight. This could mean being in an elevated location such as on a roof or in a tree, although tree sleeping can be dangerous and difficult, especially if climbing predators are around. If housing is nearby, perhaps you can utilize an attic and seal off entry points. There are many things to consider when bugging out alone, but the only sure thing is that you will face obstacles. Just make sure one of those obstacles is not a lack of a way out; having an escape from your sleep location needs to be priority. Placing an alarm system around but not near you may also be helpful. Trip wires can be used to alert, wake, and warn you of impending danger.
In an end of days scenario, there is little rest for the weary and you have to grab what you can, when you can. Hard though it may be, try not to neglect your need for rest. Staying alive is important, but so is staying energized and keeping your mind right.