I actually ran my 5k in 22:45 mins today , and I didn't feel like shit afterward I'm not a good runner at all. If you're running regularly, 8 minute mile is definitely very doable. I think once you get to 7 minutes or below that's when it becomes extremely taxing on the body.
Yes, there's lots of stuff going on in life that might prevent you from exercising, but I know people who only sleep 4 to 5 hours a night and still find time to exercise early in the morning. It's a matter of making time to do it. Now in Asia and Europe, people have the advantage of having to walk everywhere. These people are miles ahead of your typical North American.