I don’t know if people can change their fundamental personality but they can definitely change their behaviour.
How often have you tried to change somebody or have them try to change you? You can spend a lifetime trying to do this but to no avail, and this can be draining on both parties.
In order to change, the person must be willing – but not for somebody else, they must be willing to change for themselves. It all starts with understanding why the need for change and agreeing with that reason – being conscious of the need and wanting to be a better person. Then comes changing actions and behaviour. This hopefully after a while becomes second nature.
My question remains, are you just changing behaviour, which a big step in itself. Can you really change fundamental personality or are you just fooling yourself, and is this enough? Only you can decide if this is enough, each situation is different.
I would like to think that you can change personality for the better, but who knows …
“You can change only what people know, not what they do.” – Scott Adams