It’s not that people can’t change, it’s just that they usually don’t.  Making a real, substantial change in yourself requires a lot of work.  First, it requires that you accept responsibility for your own life.  Most people won’t do this.  Then, it requires that you identify a major element of your personality that is not mentally healthy for you, and decide how you want it to be.  Then you must, every day, work to break the habits that you have created.  All of this takes a lot of effort, and a strong commitment to really work at it every day.

When someone in your life has been selfish, or insensitive, or otherwise hurtful to you for an extended period of time, it is normal to hope that they will change.  We tell ourselves that because someone loves us, they will treat us better.  They won’t.  They will continue to be the person that they have always been, and will continue do the things that have hurt you.  It is totally unrealistic for you to think that tomorrow they will be any different than they were yesterday.  You can want it, but that doesn’t mean it’s going to happen.

So what can you do?  First, you must accept that this person is the way they are, and will remain that way.  Then you have to choose what you’re going to do about it.  You can choose to remove that person from your life.  If it’s a friend, or someone you’re dating, this can be relatively simple.  If it’s a family member, then it gets a lot more complicated.  Is it possible to limit the amount of interaction you have with them, or to limit the interactions to areas where you can’t be hurt or let down by their actions?

Once you’ve accepted that you cannot change someone else, and that they will not change for you, then it is all up to you to choose how you’re going to handle the situation.  This is your life.  Choose what you want from it, and who you want to be a part of it.