It's Cold In Them Thar Hills
View from my "gym" tonight - 4 inches of snow, bar freezing to the touch and I can think of many places I'd rather be!

But, this is where routine works. Workouts are planned in advance, including any on-day performance variables. Take the mind out of it - we can rationalise all types of reasons for doing, or crucially here, not doing things.
Then, just turn up for the work - rep by rep, set by set - think and plan later.