Final answer:
Russ's statement “I've been burned before” is an expression of regret for a painful past experience.
Step-by-step explanation:
When Russ says, “I'm sorry. I've been burned before,” he is expressing regret for a past experience where he may have been hurt emotionally or taken advantage of. The phrase “to be burned” is a metaphor often used to describe a situation where someone has suffered from a betrayal or a negative experience that causes them to be wary in similar future situations. This does not literally involve cooking or fire. The excerpts provided reflect various contexts where the phrase “burned” can be used metaphorically or literally, illustrating the breadth of its use in the English language.