Being flexible does not mean if you are thrown into a jungle, you can survive with all the natural resources available. Being flexible means you know how to assess the situation, process it and manage it in your best possible way that will bring the most minimal damage or the most positive outcome either to yourself and those around you. At least that is how I see it.
People can change. It's funny when they say they can't when actually they won't. Just because you were born naked doesn't mean you need to be naked at all time.
We are changing every second whether we realize it or not. Our body cells are proliferating constantly and the old non functional cells are left to die to make way for the new ones. But keep in mind, our body is not able to tolerate when too much cells replicating at a time and will end up in a cancerous state. Get the analogy?
and I hope insya Allah I will practise what I preach.