How do I handle deadlines? Easy: I panic.
Once I’ve finished panicking, I do one or several of the following:
Ask the editor if I can have an extension. Most editors allow some leeway in their scheduling. I don’t like asking for more time, but sometimes it’s unavoidable. You’re less likely to upset the editor if you bite the bullet and ask as soon as you’re almost sure you won’t make the original deadline.
Reprioritise work if possible.
Cut down on leisure activities, like watching TV or reading a novel.
I do not curtail sleep. I’ve discovered that if I work late into the night and then set the alarm early in the morning, it takes me longer to write, and what I write isn’t that great. On the other hand, if I get an early night I work better and faster, and often still meet the deadline despite having allowed myself less time to do so.
For similar reasons, I try not to cut out exercise, although I might do less of it. For example, rather than going for an hour’s walk I might do a twenty or thirty minute one instead. I do find, though, that I’m more productive, efficient and creative when I take exercise than when I don’t.