As we move through life just as we drive on a trip, we are passed by some people and pass others ourselves. Rarely do we set out on a trip of 100 miles and see the same cars the whole time. Some people stop, some drive faster, and others drive more slowly. You see drivers who come up fast and rudely pass on the right or tailgate you. You see people who politely let others in front of them.
In this same way people move in and out of our lives. We have friends now that we did not have a few years ago, and we don't keep up with others who used to be close friends. That's a normal and okay part of life.
We need to give ourselves permission to "defriend" some people who are moving in a different direction, and we need not despair if we are defriended. In fact there are some people who are not good friends, and putting distance between them and ourselves can be a good thing.
Don't keep these -- the false victim who always needs sympathy, the narcissist who only talks about himself, the downer who can find the negative in anything, the bully who laughs at others difficulties, the underminer who will throw you under the bus, the flake who never does what he says he will, and even the "super-religious" who will beat on you with the law but never speak of God's grace in the Gospel.
Then we must help our children understand these human dynamics. They often think they can be friends with everyone or even that they should just limit themselves to only one friend. The thing to remember si that no matter whether friends come or friends go, we always make these transitions with respect for others.
Begin right now praying for your children's high school and college friends, people who will influence when your influence wanes. Pray for their future spouse and for wisdom in their selection. Parenting is a lifelong but joyous process.
Blessings on your parenting,