You're a different person now, it's just sad because I miss you a lot. Strangers can become best friends just as easy as best friends can become strangers. Friends and family members evolve over time, we all do, so this is a sad but true fact of life.
This is true in relationships and also pertains to moving, having to say goodbye to family and friends, making a career change, saying goodbye to old habits/lifestyles,etc. Be Brave enough to say goodbye and life will reward you with a new hello :)