You say ' it doesn't matter ' to tell someone who is apologizing to you that you are not angry or upset , and that they should not worry .
one swallow doesn't make a summer
said to mean that, although something good has happened , the situation may not continue to be good, and you cannot rely on it
doesn't suffer fools gladly to suffer fools gladly
If you do not suffer fools gladly , you are not patient with people who you think are stupid.
sb doesn't miss a trick not to miss a trick
If you say that someone does not miss a trick , you mean that they always know what is happening and take advantage of every situation.
can't tell chalk from cheese
to be unable to judge or appreciate important differences
the right hand doesn't know what the left hand is doing
said to mean that the people in one part of an organization do not know what the people in another part are doing and this is causing confusion or difficulties