English Translation
When you can’t do what you want, you do what you can.
I’m not even going to ask whether these “se” constructs are the “passive voice se” (pasiva refleja) or the “impersonal se”. 
It could translate to the following if we want to stay as true to the Spanish original as possible, meaning to use the passive voice in English whenever the pasiva refleja is used in Spanish:
When that which is wanted cannot be done, that which can (be done) is done.