Sit near a tree or a post or even a building in an urban setting and note how much time it takes in breaths for the shadow of the object to travel a set distance. Double the distance and note if there is a difference. You can do the same for your own shade if you are standing in the sun or you can place a stick in the ground in front of you if you are on the ground. This gives you a better awareness of the day and night coming and going and the levels of sight it provides for you. You can use artificial means like the burning of a log or for how long it takes a water cup to cool enough to drink and paying attention to what is already there will open new doors for you to be able to make better decision on how to spend your time.
If you are walking in a cold weather note how long it takes your body to adjust to the new heat and wind travel levels and through this you will note your own temperature and this gives you another opening to reach control of the blood pressure and pulse.
Just like getting into the car and driving or taking your mobile phone and calling your family when some bad people arrive and they outnumber you by one knife or more it is important to build a fire before you start trembling with hypothermia or finding your way home before the sun sets and there is no light in the double canopy forest.