You're on the motorway, and suddenly hit with intense sleepiness, the next service station/exit is 30 minutes away, what do you do?

Was thinking about this hypothetical when i was driving home the other day and suddenly got pretty fucking tired. Fortunately i was a minute away from home and already in my cul de sac.

But it had me thinking, in that hypothetical situation where you're on the motorway and there's no clear place to stop coming up, what do you do?

If there's a hard shoulder my first thought would be to stop on that for a bit, but that's kinda illegal and a bit dangerous, so i was curious what you guys thought.