We do tend to tune out a lot from our usual routine and environment. We'd overload quick if we didn't. I was sitting in a seminar a long time ago taught by Eugene Albright (one of those psych gurus). We were discussing heightened awareness, and as the conversation went, I voiced an assumption that a hostile combat environment would likely induce the highest awareness level presently available, to which he concurred.

If you want to simulate such awareness enlightenment, paintball competition and various other indulgences are a good way to subliminally train the mind to achieve heightened awareness. I would not normally suggest anyone enter into real combat conditions as the risk generally exceeds the benefit, but a decent simulation will suffice most of the time.

I note that the practice of hunting can have a similar effect.

Maintaining a heightened awareness of our surroundings can be a very stressful effort. That's why our tendency is to tune out most of the time.