Unless he changes his way of behavior, he will lose his job---> If

If he loses his job, he will change his way of behavior.

the answer should be

the simple past tense of strive.

hope this !

  this riddles' answer is library.

  the "leaves" are a reference to the books' pages that the library contains; the branches are a network of libraries that connect multiple libraries' collections, resources, and items in a system of a common database, integrating them; the branches' organization are a useful management tool for coordinating the multiple collections many libraries have.