Survival
If you found yourself in a survival situation, how would you fare? Even if you never face something like this in your life, it is a good idea to be prepared for any eventuality. Testing and expanding your physical limits will equip you for existing under harsh conditions. Side benefits are things such as enhanced clarity of mind in meditation while undergoing a 3-day fast, the ability to function well throughout an arduous workweek, being free from cultural conditioning that limits us through beliefs on food, shelter, sleep requirements.
We spend large portions of each 24 hour period involved in sleeping, eating, personal hygiene, watching TV, and other frittering away of small chunks of time, 10 minutes here, 20 minutes there. How much more could you accomplish if you limit the time spent on those things to a bare minimum? Cut the time spent on these things in small increments, letting yourself adjust slowly to less sleep, a quicker morning bathroom routine, limiting TV. Periodically take a fast -- go without sleep or food or TV etc for a day, perhaps two or three.
Take advantage of the extra hours you find, to work on more of your lower priority tasks, or to fully develop a high priority task. Review your time management schedule and see how doing without some of these time-consumers, frees up time for other things.
Don't let yourself be snared by your fasts. Limit your fast to 1-3 days, once a month, and exert your Self control and Willpower to end the fast when your time is up.
You may find that your sleep requirements, for example, are higher or lower than you expected. Walking through life perpetually sleep-deprived, will cripple your higher-level thinking skills. Be sure to get enough sleep to function well. Save the deprivation for predetermined fasting sessions, or the unavoidable circumstances which deprive you of sleep. You are training yourself to deal with potential possibilities of extreme survival situations, not current realities. (unless you are living in the midst of civil unrest, such as certain areas in the Middle Eastern countries)
Take a look at your life. How resilient are you? What do you rely on daily to get make it to the next? Look at your sleeping, your eating, your entertainment, your access to spiritual settings, etc. How would you cope if that was taken away from you? If you don't know, then it's time to find out. Purposefully deprive yourself of anything you currently rely on, that you don't know how to live without. See how well you do. Can you make it through the entire time period without it? Or did you crack under pressure and addiction, and return to it. (I argue that yes, a person can be addicted to too much sleep. The human body only needs between 6-10 hours daily on average, middle age, middle health. Any more, and it's wasted. and many people can and do get by on less than 6 hours every day)
Anything which you find hard to do without, start coming up with ways in which you could compensate if you were forced to make do. Obviously, this is going to take a long time to test your physical limits. If you tried to test everything all at once, you would overwhelm your system, and come away from the experience having learned little of real value.
An apocalypse or WW III may not happen in any of our lifetimes, but then again, it may. Other events, such as natural disasters, may strike at any time. To be prepared, is to up your odds of survival. Don't wait for "some day" start preparing yourself now.