It seems that getting most of the way to an end goal is easy, getting all the way there is not. My van has been bumping and thudding and choking lately, and I just passed 295,000 miles yesterday evening. Will it make it 5000 miles more? Back at 255,000 miles 5000 was considered a piece of cake, now it's a significant hurdle, at least I fear it is a hurdle.
This is not limited to vehicles. My engineering projects certainly become harder as they progress to completion. Sometimes I report the results, then spend more than a day, maybe a couple, finishing up the official report, agonizing over "small" details. In running, I am about to have the best month of racing in my life, I hope. Yet, I still have to push myself through a couple workouts and strain as hard as I can in races.
What I have done, I now consider easy. What I have left to do, seems hard.