That person who doesn't text first? Isn't arrogant. They're just worried they're bothering you.
The person who never wants to hangout?
They're just worried their behaviour in public might embarrass you.
That one person who's always talking about their ex? They're not missing them. They just value those bonds, even though severed now.
When these people tell you their past, don't just hear them. Listen to what they're actually saying. They're saying that they're comfortable enough to open up their vulnerabilities to you and trust you. Be there for them! Don't walk out on them! They will frustrate you, irritate you and make you feel horrible, but be there for them. You will build something beautiful when they heal!