If you organize in sprints to have focus, it stands to reason that you’d have one goal.
What if that goal doesn’t take two weeks?
If you add another goal to it, you’re not focused any more, and you can’t claim you use sprints for focus. If you play Minecraft for 1.5 weeks, well, I guess you still wouldn’t have focus.
You could just declare the iteration complete and start a new sprint with a new goal.
What if that one didn’t take two weeks? And, gasp, what if your iteration time boundary stopped aligning with everyone else’s?
Keep following the train of thought. You’ll get there.