I don't like the phrase, in any of its variations. I guess it works for some kids, but it's not something I would say to my DS.
For one thing, just saying "don't throw a fit" or "don't get upset" doesn't actually teach coping skills. Maybe it's enough for typically developing kids, but DS needs direct instruction on what he should do, not just what he shouldn't do. DS is a really rigid thinker, so we spend a lot of time working on teaching flexibility and dealing with the unexpected. It's a gradual, incremental process that can't be captured by a pithy saying.
The other thing, is that the phrase goes against what we are teaching DS in terms of self-advocacy. Certainly there are times when DS has to deal with "you get what you get" and cope with that situation. However, for individuals like DS, with autism and/or other disabilities, there are many times when "you get what you get" is woefully inadequate to serve his needs. We work with him to stay calm, to explain his perspective, and to negotiate. Practicing these skills now, even over seeming trivial matters, will serve him in the long run when he needs to advocate for his needs to doctors, teachers, therapists, insurance companies, etc.
Gena
DS, age 11 and always amazing
“Autistics are the ultimate square pegs, and the problem with pounding a square peg into a round hole is not that the hammering is hard work. It's that you're destroying the peg." - Paul Collins, Not Even Wrong