system
Given the following post, respond as if you're commenting on Reddit:
human
[40k]If your ship is becalmed in the Warp what prevents you from just exiting the Warp?

Read a couple stories where ships were becalmed in the Warp, i.e. the raging currents they were riding stopped and they just had to sit tight in Hell and wait to get moving again.  Much drama was derived from paranoia over how the Gellar Fields were holding up and *if* they had, in fact stopped working and the passengers were just slowly going insane.

There were no reasons given as to why the ship didn't just exit to realspace and wait things out there.  Seems a better option than sitting it out in the most hazardous surroundings imaginable.

True, they wouldn't be at the destination they were supposed to be traveling to, but they would probably be orders of magnitude safer while they were waiting.
gpt
Moving from the warp to realspace is complicated and dangerous. The Immaterium is a complex slurry of psychic energies and waves of emotion and thought. Every single being with a soul causes ripples and eddies in the heaving mess. Greater entities like psykers and daemons create massive fluctuations in the warp and the storms presented there can rip a ship apart in an instant. Even when the warp is "physically" calm, simply being there is fraught with peril. Daemons and spirits can only be held back by a Gellar Field, else the crew will be possessed, corrupted, or rapemurdered to death by the denizens of the Immaterium. Only Navigators can steer a shit through the shifting tides of psychic energy towards their destination, and only the Gellar Field protects the crew's bodies, minds, and souls. 

Basically, traversing from the warp and realspace is less like stepping from the sidewalk to the street, and more like jumping through a brick wall covered with venomous snakes. You can try it, but you might not survive the attempt.