I believe I now understand your fear.
In a way, it may not be too far off mine; both revolve around the idea that anything short of the desired denouement–whether four, five, six years, the rest of life–is failure, a footnote to a gross caricature of a hero’s journey: too much abyss, too little progression. Life, after all, is not wont to hand out consolations: no, no one is going to congratulate you for making it that far, make it til the end or bust (and bust hard). Nothing to celebrate, move along, keep grinding it out, because nothing gets better anyway, and anyway your sacrifices did not see you to the end, until nothing makes any sense anymore. Until one day, we wake up to our realizations, which will be so crushing that they will keep us in our beds: you beside that which you’ve failed, I with that which I’ve failed inside.
And nothing will have been worth it.