Short and sweet.
Although I do try to mix it up to some extent, all I want is for each session to get the same result- Better than the last time. That's all I ask of them. I don't over train what they already know, and what they learn is rewarded, perfected, then on to the next level.
They honestly never get bored or sour, because I'm always amping it up each time. They're always learning, and wondering what's next.
Of course we have our break days where all we do is hack around the pasture at the trot on a loose rein. That's always nice.
On the work days, I never feel the horse is repeating anything to a drilled extent or getting sour. My gelding is always happy while I tack him up and never resists a ride, so that alone, tells me he's good with the training routine. If he ever resisted walking through the arena gate, or just flat quit trying at each ride, then I might want to rethink my plans.
Even on groundwork, his pivot, sidepass, ground drive, back, etc..All that could still have some perfecting done. There's always something new to do.
"You're just as sane as I am."~Luna Lovegood.