The question is not so much “Can I run a marathon?” as “Will I put in the miles in training?”
If you plan to run more than one you quickly come to “What will make me more likely to show up and train?” and on to “Where can I find pleasure in it?”
So you move from chasing the medal, the people and a finishing time to chasing the path, thought, and the day.
The pleasure of the thing itself might be the hardest thing to teach, but it’s the thing that matters most, because it’s what will bring you – bring them – back.