I've started a new playthrough a few weeks ago, almost got a bout of PTSD at the memory of that escape sequence. Originally once you got on your horse you would be peppered with arrows and often bleed out before you got even half-way to Talmberg, or you just got killed the moment your horse ran out of stamina. Which happened multiple times as you couldn't let stamina regenerate fully before you had to start a new gallop and while trotting along you just had to hope those Cuman archers would miss their shots or you'd be screwed.

It's definitely a lot more doable these days, didn't had any problems this time. Just as long as you remember to gallop and keep it up as long as possible. But the lack of obvious directions underway can be confusing, make sure to listen carefully to Henry's comments. >!And of course don't bother to engage the Cumans once you leave the castle, if you want to help Theresa just whistle to get the attention of her attackers while keeping on running to the horse conveniently parked a little bit further up ahead.!<