Rispento comes from spegnere ("to turn off" or "to extinguish") and means "turned off again." In the song, Laura Pausini sings about repeatedly turning lights on and off during a sleepless night, creating a memorable image of emotional restlessness and longing.
This is a breakup song sung at the exact moment the other person has gone. "La notte si è appena spenta / E sono qui senza di te" (The night has only just gone out / And I'm here without you). Laura Pausini doesn't rage or beg. She describes a strange arithmetic of absence: "Più te ne vai e più ti sento" (The more you leave, the more I feel you) and "Più non ci sei, più sei con me" (The less you're here, the more you're with me).
The verse is where she gets stubborn. She admits it took her ages to love him "come sei" (as you are), says she'd need "un'altra eternità" (another eternity) to get over it, and plans to bury herself in work by day. Then the flat refusal: "Io con un altro no, io con un altro mai" (Me with someone else, no, me with someone else, never). The chorus hangs on one long word, immensamente (immensely), repeated so often it becomes the whole song: "Mi mancherai immensamente" (I'll miss you immensely). A nice detail for learners: "ho acceso e rispento" (I switched on and off again) uses the prefix ri-, Italian's way of saying "again", and pictures her flicking lights on and off through a sleepless night.