I was also taught that children should be seen and not heard, that Communists were dangerous, smoking was cool, steaks would make you healthy, apartheid was sensible, if you spared the rod you spoilt the child, you were a loser if you didn't go to University, get a degree and find a steady job, people without degrees were stupid, women should stay at home and cook, look after the kids and do the housework, men were more capable of looking after themselves and their families than women, you shouldn't have sex out of wedlock and you certainly shouldn't be born out of wedlock.
These were a few of the beliefs of the political, educational, economic and social systems in which we lived at the time. All of them have been challenged and shown to be what they were: beliefs without foundation. (And funnily enough I can't find anyone in South Africa now who will confess to ever having harboured any of those beliefs.)
Anyway, the point is that once particular beliefs have been put in place by the systems, we find ourselves constrained to conform with those beliefs. Our behaviour is then moulded by them and our creativity and ability to live life fully is suffocated out of us.
It is incumbent on us to test every belief we have for validity, no matter how "true" it may seem in the moment. When we act on unverified beliefs, rather than on the verifiable data which Life itself gives us, we end up excluding life as it and rather living it as we think it should be, or as others have told us it is.
And how do we verify anything? Simply acknowledge what the actual experience is. What is the real hard experiential data? That is the rock on which we can build our actions.