As Christians it is important that we know that God loves everyone unconditionally. And that God wants us to love our neighbor as we love ourselves, and even love our enemies no matter how difficult. And even if that neighbor or enemy doesn't believe in God, or follows a different religion, it is not "us" vs."them."
I've been in enough church's where I've heard the preachers up in the pulpit going on about atheists, homosexuals, Muslims, or "fill in the blank"... and with that mentality of "us vs. them." I've seen it enough times to know it exists more than it should. And then they wonder why they aren't "winning" people over to Christ... why their congregations aren't growing... I've been in church's full of petty people, where it just felt like high school all over again... Ignored and shunned for my mistakes in life... I didn't "fit in" with the crowd. I've seen it so much that it was amazing to me, an absolute shock, to sit it a church where this didn't happen... where it was the total opposite...
Teaching us to apply scripture in our personal lives... to forgive over and over again, not just for the person needing the forgiving, but for our personal healing... and reaching out to the possibility of non-believers sitting in the congregation that morning, and welcoming them, expressing that they are loved and not preaching against them, but showing them what a Christian is supposed to look like. And this church is growing and people are coming to Christ. And it is because they want people to know who Christ really is. They want to reach people and let them know they are loved.
It is not up to us to choose who "belongs" - as Christ followers we are supposed to love, welcome, and accept everyone. By doing so, applying Christ's teachings to our lives, and showing through our actions what a Christian is supposed to look like, that is how others find Christ... through us.
This is one of the hardest ones to apply. God wants us to forgive, because he has forgiven us. But when people do us wrong it hurts, and it's hard to just forgive and let live. But even if you have to forgive one person 77 times, forgive them. It may take a while to forget, but eventually it won't bother you any more. And by forgiving you will be set free.
I can hold a grudge with the best of them... but holding a grudge is like a delicious poison... at first revenge seems like it'd be so good. You go over in you head what you should of said to put them in their place... you think about how to get them back. But this only makes things worse. It eats at you. If you are still holding a grudge against someone who hurt you today, let it go and strive to forgive them. A lot of time it is just petty stuff, and even if it isn't petty, you've got to forgive because Christ forgives every one of us for every stupid thing we do.