Negotiating salary advice

Basically I got offered the position I want, and I was offered the exact number that I want. I said 75k-85k, and they gave me 80. I am happy with the number, but I was wondering if I should negotiate for more? Should I risk it and negotiate when I'm already happy with the offer? And I'm not really sure I have much support to defend my case if I were to ask for more, but I always see advice online about how to never settle on the first offer.

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