So when you say 'I must go on, I can't go on, I'll go on', so, is it that the last clause, there, modifies the previous one? That you thought you couldn't go on, but that on reflection you've realised you can? Or that when you said 'I can't go on' you actually meant 'I'd rather not go on'? Perhaps the circumstances changed, such that before you couldn't go on, but now you've discovered new reservoirs of strength and have revised your former opinion?
What has this text to do with before and after, with revision, with going on. Going on is the point where it stops