People are versatile beasts. Ever notice? Humans can do a lot of things.
They can have all kinds of different appearances, characters, and lifestyles.
  Some people also seem to be very changeable. Their behaviour changes from
day to day: One day they seem energetic and lively, the next they may be
relaxed and toned-down. Some of it is involuntary, brought on by mood or some
other volatile factor. And some of it is brought on by conscious, deliberate
effort to change one's own behaviour.
  But for all the posing one may do, trying to present themselves as
something they're not, their true nature shows through eventually. A person
can act differently for a while, but they can't maintain a facade forever.
From day to day, a person exhibits a habitual pattern of behaviour that
reveals their true nature.
  It is said that "A leopard never changes its spots", meaning (in reference
to humans) that a person's true nature never changes. This is not *entirely*
true, as a long period of time can indeed change someone's nature; But, as I
say, it does take a long time, and a lot of effort (or else a powerful
circumstance) to make someone really change. A person's consistent manner
reveals what they really are.
  You cannot judge a person based on seeing them once or twice. You can draw
some basic conclusions, perhaps, but to really know someone means to know how
they act. A person may say they have changed to others; Indeed, they may even
believe, in their own minds, that they have changed. But time is the ultimate
test.