You may be replaceable to a lot of the people who have left you, and maybe most if not all of them have been replaceable to you. But to some people that you may meet, you are not replaceable, and there are some people who you may meet who will not be replaceable to you. So be very careful only to cut out those people in your life who are toxic or bad people. Do not just cut people out willy-nilly, because someday, you might need them and they might need you.
And in general, we are stronger as individuals when we have more good people in our lives to help us, to support us, and to encourage us. Having more good people in our lives gives us a place to turn when we need someone not just to talk to but to OPEN UP to, to trust. It gives us protection against feeling alone. I believe the world would be a better place if we kept good people in our lives. We are social beings, even the most introverted among us like me.