This one made me go digging through memory and wikis — and honestly, it's a little fuzzy because there isn't a well-documented, widely-cited set of canonical lines attributed to someone named Alyssa Targaryen in George R.R. Martin's main texts or the HBO adaptations. If you meant a different Targaryen (like Alysanne or Daenerys), then there are plenty of memorable quotes; but for an 'Alyssa' specifically, most of what people refer to tends to be fan-created or appears in minor, non-quoted mentions in appendices and histories.
I usually start by checking sources like 'Fire & Blood' or 'The World of Ice and Fire' histories and then cross-reference with fan wikis or episode scripts from 'House of the Dragon' when names get murky. If 'Alyssa' is a character from a fanfic, roleplay, or a lesser-known tie-in, the best route is to point me to the exact source (a chapter, a fan post, or the episode timestamp) and I can pull quotes directly. Meanwhile, if you just want Targaryen-flavored lines people love, I can list verified quotes from better-documented Targaryens — for example, Daenerys’ dark, famous line about taking what’s hers: "I will take what is mine with fire and blood," and the clipped command 'Dracarys' which has become iconic.
If you want, tell me where you saw 'Alyssa' (fanfiction, a wiki, a game mod, or a passage), and I'll track down exact, attributable quotes. Otherwise I can compile a list of notable Targaryen quotes that capture the same vibe.