out of the overflow

How we appear to others can be different to how we feel inside. That's why people's behavior sometimes seems strange and inexplicable - they're responding more to some inner drama than to what's going on around them, and we can't see that inner drama.

When people speak to us, especially people we don't know, they aren't really talking to us, they are talking to what we represent in their world. For Christians, other people should represent their neighbor or even Christ himself, and we should talk to them accordingly. 

The Bible talks about the fruits of the spirit - the qualities that the holy spirit will bear in your life: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control (see Galatians 5:22-23). They aren't like KPIs, where you strive to meet the criteria. No, they are qualities that will grow naturally when you have a relationship with God and they are qualities that are reflected (or not) very clearly in how you speak to others.