The most valuable things in life (e.g.: friendship, courtesy) cost nothing.

(idiomatic) Someone or something that entirely satisfies the expectations of everyone, no matter how diverse and conflicting those expectations may be.

If an unfortunate event has already occurred twice, a third unfortunate event is likely to occur.

(an expression of) the doctrine that all knowledge is subjective, being derived from observations made by humans, and there can be no objective truth

Things are not as bad as they seem.

If a fortunate event has already occurred twice, a third fortunate event is likely to occur.

Alternative form of one of those things

Alternative form of all things to all people

Without considering or being affected by external factors.

When finding oneself in a troubling situation, one should first make sure one is not making the situation worse by his own actions before addressing all other causes.