Do you think that, deep down, Severus wanted to be happy ? :)
…this is such a nice question, and I fear I’ve only got a miserable answer.
I think when Snape was a kid, he did want to be happy.
I am certain he didn’t know how to achieve it, and that’s why he was drawn to power instead. I think he thought power would mean he would be respected, and then he could make sure that nobody stopped him from achieving what he wanted…and then he could be happy.
Personally, I read him as a kid without power, both at school and at home, and I think he was easy pickings for the Death Eaters to recruit. I am really unsure about what was going on in Snape’s head when he defected - I can’t decide whether he was already disillusioned with the Death Eaters and Lily being threatened was the last straw, or whether he was just so appalled by Lily being threatened, he threw in the towel.
…but as soon as he defects, I think Snape stops wanting anything for himself, really. As soon as he puts Lily’s life before his own, that’s the end of Snape and his aspirations.
His role of spy, which he knew he would have to return to, meant that he couldn’t change career. He couldn’t marry, or have any meaningful long term relationship, or have children. He was stuck in limbo, playing a part.
Once Voldemort returned, he then spent his time between two masters, doing whatever he was told and doing his best to survive.
So the sad answer is, I don’t think Snape really dared think about being happy; I don’t think he aspired to anything, because he knew that until he’d repented…until his mission was complete, his life wasn’t his own.
There is, of course, the awful irony that all of the things Snape achieves are all things that I feel both he and Lily (as kids) would’ve admired. He becomes a young Slytherin Housemaster, a successful teacher, and ultimately Headmaster.
If someone had given him those options at 13, I think he’d have happily taken them, and not aspired to be a Death Eater…yet, even more ironically, he wouldn’t have achieved any of it if he hadn’t been a Death Eater in the first place.
And that, to me, is Snape’s deepest tragedy.
(Oh well, that was depressing. Eeeesh. Sorry, mate.)