It's 10PM on a weekday. After a long day at work you go cycling, 12 kilometers to the seaside. Not because you want to, just because you think you should. It's a cold winter day, with the temperature around 4C. A dark night. No moon. Let's go.
40 minutes later. You turn from the main road into a narrow path that leads to the beach. It's pitch black. No lights, nobody there. No sound except for the smashing of the waves. You take a break.
10 minutes later. You've started on your way back, and shortly after departing you've realized something. You've had a big tailwind going down to the seaside, and now an icy cold wind is blowing in your face. The way back is twice as hard, going ever so slightly uphill. Not enough to pose a serious problem, but enough to make your muscles hurt after straining them for 40 minutes on the way to the seaside. Your body is tired. The wind is cold and strong. In your mind you are already home, taking a nice hot shower, but it's impossible to concentrate on that for longer than 5 seconds because of the fatigue. You're losing strength and willpower.
Then, two kilometers later. Acceptance. You no longer feel the pain. You no longer have the energy to imagine yourself being at home, but somehow your body and your mind focus on one thing: the road ahead of you. You find your rhythm, and you enjoy. No break is necessary, everything comes naturally. And before you know it you're back home, and you wish that you could have continued longer.
You are satisfied.