How does one change their personality to be more open and friendly?

I have ALWAYS been negative and don't trust many people. Is it possible to change my personality after 40 plus years?How does one change their personality to be more open and friendly?
you will have to be proactive at being friendly. When you see an opportunity you will have to say to yourself, okay...How can I say something positive/uplifting... As for being open? That may be a little more difficult. It's certainly not always wise to be open, but if there is a trusting and committed relationship in which you are closed of to the person, the try it one step at a time...you have to adapt to it...there's no easy way once you've been burned. You may have to weigh the options, whats the worse that can happen-will it destroy me? and on the flip side, what's the maximum benefit from this situation? Is it worth it?How does one change their personality to be more open and friendly?
You've already hurled the largest obstacle by recognizing and wanting to change your behavior. Its not easy, but it can be done. (Mine didn't change until age 50.) Just start seeing the good in things and minimizing the bad.
I agree with the answerer above me. You're already one step in the right direction. People can't change something that they don't see as a problem but good for you, you are on the right track.