Shark

You're good at this. You just don't give up. Swimming along the shores with an innocent human being while depending on tiny fish and flesh to keep you alive. Not the flesh of other people, but the flesh of a single individual helps you quench your thirst. With just one bite you've fallen in love with the special qualities and taste that no other trout has. But you get sick of the same taste, and beg for variety; swimming away to rid yourself of hunger while leaving the defunct person to lay floating across the ocean. About to pull for air and safety, she makes a halfhearted attempt to stay alive and the shark swims by once more only for another bite. She tries to swim away as fast as she can but this great white beast clings heavily onto her side like a tick, dependent on their victims. You aren't needed here. You take life away from something that helps you live. The only thing that can push her to safety are the soft waves of the ocean, and maybe she can walk away with a just a scar from past injuries.

Swim away and never come back.