"
screamin' at me, "Take her now!
This is your only chance, won't get another, don't let me down!
Don't fucking whine
Jeremy has, at this point, kidnapped the object of his affections. His evil side desires her to be his and only his, so the evil monster is trying to get Jeremy to go after what he wants. Since the demon and Jeremy are basically the same person with the same desires (but with the demon having a more glorified version of said emotion or desire), it's basically saying, 'hey, you want this, and so do I, so you need to take the only chance you have to have what you really want."