If i had known then ...
It's very easy to get into a negative spiral and kick yourself over opportunities missed, two of my very earliest blog posts touch on that topic. Add in the aspects of 'If I had known then what I know now' and it could get very messy from an emotional and practical view.
Occasionally conversations with people can bring your own concerns and disappointments into stark relief, but equally can be just as problematic further down the line when you realise they reflect on your own problematic relationships with things (such as a conversation between two former professional dancers about how vocational training in the 80s and 90s created a whole generation of dancers with really toxic attitudes to food - and how behaviours developed then impact for life - and then seeing your own problematic attitudes towards food in those behaviours).
There is little to do about missed opportunities, other than to look out for them to come round again and seize them when they arise. Along with that is look long and hard at why and when you get no for an answer from people or organisations. 'never take no for an answer' is ultimately counter productive, but ' always question a NO ' is a productive midset and leads you to queastion all sorts of things