To me Sara was angsty in Seasons 1 through 3. 4 too probably. That's what I called her then. Ms. Broody. And that's why I liked her. Her darkness. When I look at her I dont see sunshine. I look at her and I see destruction.
She's got a dark past but didn't really talk about it. Instead she submerged herself in her work, have close to zero personal life and when cases hit home, she took it very personally. I think her darkest moment in Season 4 was in the episode Committed. Then in Season 5 she slowly unravels herself and in Nesting Dolls we saw her break down to pieces. Season 6 went like a blur to me. But it seemed to me like she gets happier and happier (smiling more, looking radiant, having a life) as the season progresses. No more the brooding Sara I once knew. Season 7 – I think she's happy now. Probably because of G, and other reasons we know not of.
In Season 8 if William Petersen chooses to leave so G's not there, I wonder if she'll revert back to her brooding days. I think not. She's tough. She dont need no man. But its all up to the writers. If they make her all damsel in distress...thats the end.