Focus is the same as ammo, energy, or dare i say... mana? (I've not played a jedi char yet)
If so, and you are running out often, you may need to work on your "rotation." Alternate in skills that have low or no cost. I know as a vanguard tank, and on my smuggler healer, it is easy to use up this pool and not be able to use any worthwhile skills for a while, rendering you almost useless in the meantime.