"hang in there"
how do i say "hang in there" or "don't give up"?
"No te bajes los brazos" - It is a colloquialism from Argentina, at least in Buenos Aires. It literally means don't lower your arms. I believe that it is a reference to Moses in a biblical story where as long as he held his arms up the Isrealite army would be winning, but if he would lower his arms they would start to lose. So, if you don't lower your arms, you will eventually win.
Of course you could always go for the more standard, no te rindas, or no te des por vencido(a).
"No te rindas", or "No te des por vencido/a"