The leopard and it's spots.
It's hard to believe that people do change, especially after you give someone a second chance and they go right ahead and do the same thing all over again. 'A leopard never changes it's spots' is a saying I'm sure we are all familiar with. But what really are these 'spots'?
As a person who has gone through a remarkable change, and is probably still changing, and will probably continue to gradually change till I die, I should probably state that I absolutely believe in the leopard changing it's spots. It's been said that we all have an evil side, and when pushed to the limit in given situations, even Saints would react in a way that would shock even the most shameless sinner.
What is change really if not focusing and building on the traits you want to develop and continually saying no to the ones you want to do away with? We all have it in us; the potential to be very good and also very bad, it's just a matter of the stimulus.
So if someone has been on the straight and narrow for a good while, trying to change and become a better version of themselves, don't count them off. These things take time. Just because their evil side hasn't reared it's ugly head in a while, doesn't mean it died a natural quick death. And just because they slip and unfortunately fall back into an old bad habit one given Saturday, doesn't mean that nothing at all has changed.
It's all about perspective. What you get is what you see.