Familiarity means ‘close acquaintance’. In human relationships it may lead to undue intimacy, as when a master treats his servants with so much laxity that they regard themselves as his superiors rather than as his inferiors. In another sense, familiarity can cause us to look on really important things as being of no account; we know them so well and enjoy them so often that we accept them without gratitude or thankfulness.
If we do a thing many times that it becomes a habit, we are liable to get careless. For example, a spiderman, one who works on high buildings in course of erection, may become so accustomed to walking along girders that familiarity breeds contempt and one day he misses his footing and falls to his death.