What do you think greene meant when he said ‘the success of the day seemed to be doubtful for a long time? ’

I think he meant that to be successful is to try without which implies that every time you wake up you do not think or wish about being successful it just happens without any second thought.

He didn't expect anything productive to come of the day because it had been later before they saw any progress.

I have not read the main source but this statement I assume means, something along the lines of what I have said
I really hope this helps you :)

The led the formation to the united states