Maybe in an extreme case I would seek revenge, but I would see it as an obligation, an obligation to repay a wrong, and I would do it with a clear state of mind, and not allow it to do harm to myself. With a clear conscience and with a clear state of mind is essential I think. Like Nietzsche said: "who ever fights monsters should see to it that one does not become a monster in the process". That's an excellent perspective to have (and that quote has interesting and immediate relevance to Angel in S3-S4). The quote finishes: "and when you look into an abyss, the abyss looks into you". In other words, the self tends to turn in upon itself when you think hard upon yourself, like a snake eating its tail, and can often bring about nihilism and self-undermining. The quote also has a metaphysical implication, but I'll leave it to everyone else to consider on their own.