“You’ve got to grind, grind, grind
At that grindstone
Though child’ood slips like sand through a sieve
And all too soon they’ve up and grown
And then they’ve flown
And it’s too late for you to give”
The turning point for Mr Banks in Mary Poppins is when Bert manages to get through to him. The change in the man is amazing afterwards. I see so much of myself in pre-epiphany Mr Banks and Bert, as they represent being not aligned with TMTWGR and being aligned with TMTWGR, respectively.
The companion movie called Saving Mr Banks demonstrates how the main message was always about Mr Banks as opposed to Mary Poppins. Definitely worth a look.