That is what I meant when I stated the AFM/FCOM is not the
be-all and end-all for experienced professionals, despite the
long-winded bloke above who I assume asserts the opposite
Leaving the childish insult to one side (does the OP want a comprehensive, clear, answer, or words on the back of a fag packet?), I have already said that there will be odd occasions on which the proscribed procedures must be set aside.
you may deviate from it for the immediate purpose of ensuring the safety of flight, but this should be a very unusual occurrence, not a routine one, and should be reported.
Have you heard Art Stacey, who ditched his Nimrod in the Moray Firth, speak about his incident? He gives a salutary lesson in airmanship over the niceties of CRM...
BUT, those occasions are very few and far between - in twenty-plus years I have only experienced a couple in normal line flying. That said, I have been flying with very good procedures; those with fewer procedures or bad ones will have to deviate more often.
Disregarding the Ops Manual or AFM is to be done on personal risk, and either (a) you will have to account for what you did and why, or, (b) the investigators will be VERY interested in what part your decision made in your death (and possibly those of your passengers).