for all x, p, and q, it is not obligatory that if x(p) then x(q)

or equivalently

for all x, p, and q, it is permissible that x(p) and not x(q)

where obligation and permission are the equivalent of necessity and possibility in deontic modal logic

Well, I am not sure if my formalization is correct, let me know.

If we denote by Gx the predicate that says: Good for x.
And let L - denote the necessary operator.
Then I would write it as:
\forall x \forall y (Gx \rightarrow (~(x=y)^ ~LGy)

I think.

where ^ stands for the conjunction connective.

I think a more adequate formalization would be ∀x∀y(◊(Gyx∧∃z(¬Gyz∧z≠x))), that it, for any x and y, is possible that (y is good for x and there exists a z different from x such that y is not good for z). This means that for anything that is good for you can be person for which it's not good.