If a tree does not lose leaves, then it is not growing. The shedding of leaves is a sign of growth in a tree. And the loss of friends and associates is a sign of growth in a human. Just as you outgrow clothes when you grow, so do you outgrow people when you grow.
Don't be surprised when friends leave you when your are growing, it is part of the development and there is nothing no one can do about it. In every stage in life, you tend to find new friends, if you are not around people who share the same value with you it would be hard for you to grow, in order to overcome this you had to let some friends go, so that you can easily transform to the new person you had love to.