Symbolism, Imagery, Allegory
Clarissa is full of dreams that give us clues into our favorite characters' internal states. Check it: before deciding to run away with Lovelace, Clarissa dreams the dude "carried me into a churchyard; and there, notwithstanding all my prayers and tears, and protestations of innocence, stabbed me to the heart, and then tumbled me into a deep grave ready dug, among two or three half-dissolved carcasses" (84.3).
Gruesome. There's definitely some foreshadowing going on with all this dream imagery, and Clarissa knows she should be paying attention to it. After all, she knows perfectly well that Lovelace has a rep for ruining girls' reputations. Those "half-dissolved carcasses" don't bode too well for our serial seducer. Still, it's telling that Clarissa can't help but keep the correspondence with Lovelace going. The dreams tell her everything she needs to know, but she still can't get enough of her boy.
Livin' on a Dream
Lovelace's dreams could definitely use some Freudian analysis. Usually, the guy manages to keep his emotions on lockdown, but his bad deeds come back to bite him when he hits the sack. In fact, we know that Clarissa thinks that nightmares are a divine punishment: "By God's grace I shall be easier tomorrow, and especially if I have no more of his tormentings, and if I can get a tolerable night" (440.10). All we have to say is: if Clarissa thinks she deserves nightmares, what do you think Lovelace deserves?