The following didn't actually happen, but it's a good summary of current events:

"Hey."
The young man looked up from his reverie, noticing that his friend had just spoken to him. "Hey, what's up?" he asked.
"Nothin' much." His friend replied. "What's goin' on with you?"
"Not much, just sitting here, alone, until you showed up. I'm..." The young man seemed to be at a momentary loss for words.
"You're what?" His friend asked.
"I don't know. Just bored, I guess."
"Somethin' bothering you?"
"What do you think?"
"Oh, that..." Now his friend was at a loss for words.
"Yeah, just a little on edge maybe." He explained, practically gritting his teeth.
A slightly confused look passed over his friend's face. "Why... no, I know why it bothers you, but, should you really let it get to you like that? I mean, it's not even your problem."
Now he really gritted his teeth. "I know. It's just... it shouldn't be a problem at all!"
"Whoa, man, no need to yell, I'm right here."
"I know, I'm sorry. I shouldn't let it get to me. It's just that it's such a huge change and...and..."
"And you can't help."
He steeled himself. "Yeah." He said in a huff.
"You don't even know what it is."
"I know... not knowing things always gets me into trouble. But I can't just give up. She's my sister."
"Maybe you should just take a break. Let whatever it is take it's course. She'll come around, I just know it."
"You're probably right. She's always been strong. If she still has a fraction of the strength she had before, she'll overcome it. I should just not worry."
"That's right you shouldn't. You've already said what you felt you needed to, you don't need to worry."
"You're right." he said, breaking a small grin for the first time in what felt like ages. "Thanks."
"It's what I'm here for Dave." His friend told him with a pat on the shoulder.