Once upon a time, a woman was picking up firewood. She came upon a poisonous snake frozen in the snow. She took the snake home and nursed it back to health. One day the snake bit her on the cheek. As she lay dying, she asked the snake, "Why have you done this to me?" And the snake answered, "Look, bitch, you knew I was a snake."
For those who may not know, this was in the movie Natural Born Killers. I'm sure there are any number of takeaways you can get from the story but I think it illustrates how we often want things to be a certain way and then seem surprised when they're not. Far too often we can convince ourselves that our intention or our desired perspective is how things should be. This is not only wrong-headed but dangerous in many cases. You have to deal with life as it is, not as you wish it to be.
Another thing that I'll point out is we need to be sure we aren't expecting someone to act counter to their nature. The snake is going to do what snakes do and to pretend that you somehow can change that is hubris at a minimum. It's similar to the spouse that believes they'll be able to change the person they married into the person they want them to be. I'm not saying people don't change, but you can't be the one to change them just because it's what you want.