This is how I'm able to out for a quick jog/run and come back two or three hours later. My brain just switches to engineering mode and I start thinking about circuits, op amps, code architecture, milling, 3d printing, stories, plots, arguments...

Once I get past the "why am I running?" phase and my brain clicks over (usually about the same time my body switches from anaerobic to aerobic energy production), I just disappear into thought and time vanishes...