Miss this train at the last station

The train was about to pull out of the station. Swinging a large bag, a young man managed to reach the train, throw his bag in and climb aboard, gasping for air.

Seeking at him, another man said, "Young man, you should be in better shape! At your age, I could catch the train by a gnat's whisker and still be fresh. Look at you, panting away."

The young man took a deep breath and said, "Pop, I missed this train at the last station."