Self-prescribed blindness

There is this proverb in Polish, I have no idea if English has an equivalent, something like "hell is paved with good intentions." I have been wondering how often we use this excuse - "but I meant well", or even childish "I didn't mean to..." It may well be true that we have the best intentions and screw something up anyway, for different reasons - maybe our idea of what was supposed to work was a big misconception? But my question is how often do we say something like that and it is meaningless, or worse - a big fat lie? How many times do we say it to lie to ourselves and how often to others? When it is less painful? How easy (difficult?) is it to convince ourselves or somebody else that we do mean well...
If we really knew ourselves, would that knowledge be helpful (and for whom?) or rather a burden? If we carry some kind of standards within our minds, uniquely developed throughout each person's life, then our self-perception can never be objective anyway. It will unavoidably be a reflection of what we think, feel, and want. When somebody "opens our eyes" to some part of our disposition, is it truly that we get to see what we refused to see before or we are just accepting this person's perceptions/standards/experiences? If most people have only a vague or highly idiosyncratic idea of who they are, is it possible to truly bond with anybody? On what level?
It seems that what we get are only little fragments, shreds of random connections, these sweet little moments of euphoria because it feels, even if only for a short while, that we are understood although we don't understand. That we are accepted although we don't accept. That we are not alone although, eventually, we always are...