one of my least favorite pop phrases, "It is what it is." (it's massively annoying, that's what it is). (right up there with "Everything happens for a reason." - delivered thoughtlessly, tritely and trivially in even the most horrific of circumstances) but, there is some truth to the cliche (there usually is). I prefer this perspective on "It is what it is."
“Accept – then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.” ―Eckhart Tolle
whatever the situation one finds oneself in at a given moment, it certainly is a present reality ... and, it must be embraced as that, and dealt with ... the sooner dealt with the better. and, frustration won't change the event. while "It is what it is" may sound like the non-thinkers version of being "passively realistic" (it does to me) ... acknowledging the present reality, and choosing to work within that reality, is certainly the most practical approach.