English Translation
Strive to be happy.
The way Carla says it (“sforzàti”) , it sounds like the translation of “Compelled to be happy” (plural masculine).
For the record, it should of course be “sfòrzati”.
Edit: Come to think of it, “Compelled to be happy” would be “Sforzati di essere felici”, so Carla is also being ungrammatical.