When to ignore the principles
The rules for what starting hands and cardodds you should play, of course, varies dependin on the situation.
If, for example know a player well and see that this has a weaker hand than he seems to pretend to have one can of course call,
even if you do not have the best hand yourself.
And in the same way you can sometimes take a chance and raise even if you do not have hit on a drawing hand,
but in the long run bluffs, sooner or later are called and then it can be expensive.