Most pilots, even PPLs these days (due to GPS etc), don't navigate enough with compass, stopwatch and map to realise that with a bit of experience it's uncanny how accurately you can do it.
I used to regularly fly hundreds of kilometers over featureless African bush and swamp with the GPS switched off for the practice. I was struck by two things:
(a) With practice you quickly 'sense' after setting course how much drift you have and how much to correct by. After flying regularly like this for a bit you get an intuition for it; no need for fancy mental calculations.
(b) If you fly the same route enough, even if it is featureless, you know where you are simply by such things as slight changes in the colour of the ground etc.
However, technological aids (which I am all for by the way) mean people rarely fly enough the old fashioned way to get really good at it.
Golden rule of course - stick to your heading like glue unless youhave reason to change it.