What's the most important part of BE?

There are three major parts: RO, RI, TOL. Next to that there are some important integration exercises, as I would like to call them. Lipslurs (snaps!), staccato(zips!), double tonguing and crescendo-decrescendo tend to coordinate and integrate the muscle movements learned in RI, RO and TOL.In the process you will find out which part is the most difficult to learn. This automatically needs the most attention.This does not mean that the other parts are not important anymore. You should always try to balance your practice of BE which means that all the parts get attention.