Writing is easy.
Someone who is passionate about writing will never have trouble actually writing. Sure, they might get distracted or temporarily lose track of the plot, but when it boils down to deadline-or-nothing, they’ll (nearly always) pull through with their work. It’s not the actual writing that can cause trouble. I won’t go into procrastination again because that horse is long dead round these ‘ere parts, but sometimes someone in the vicinity might need help or you’ll need to actually go and eat or watch your favourite unmissable TV series. That’s not the problem.
What if there’s no procrastination? What if you’re genuinely working on a piece of brilliant writing and suddenly, you don’t know how to connect the dots? Forward planning is something most writers do (as opposed to the organic approach – dibs on ‘Organic’ by the way guys) so occasionally the bridge has to be built to fix the bits between the concrete events in your prose.
Say that your character needed to return home, but there’d been a flood and they needed to get back, but you hadn’t yet decided how they got there. Boat? No, it’s a flood, not a casual stretch of water. Hot air balloon? It might be a wartime story, therefore a hot air balloon is likely to get shot down. Teleporter? Piggyback ride? Eventually you break out into a point of utmost frustration.
That’s when to take a break.