When the detailed, repetitive filling starts to wear on you, the trick is almost always in changing the way you approach the work rather than just powering through it. For me, the biggest help was to stop thinking of the piece as one continuous object. Instead, I break down the dense areas into tiny, manageable zones, maybe just focusing on filling in the leaves for ten minutes then moving to the background filler for five. This gives your eyes a chance to rest from the same curves while still contributing to the whole design. It feels less like a monumental task and more like a series of small wins.
One workflow change I found really effective is to switch up your materials even within the same segment. If you have a section that needs dense satin stitching, try alternating between two slightly different thread colors that are in the same family, or maybe switch to a slightly different satin stitch density for a few rows. Even a tiny variation in thread texture or sheen can trick your brain into treating the work as new, wich helps reset that repetitive feeling. It gives you a small sensory shift.
Another technique that works well is to dedicate a specific amount of time to a non-essential element. If the main figure is the source of the burnout, try dedicating a work session entirely to embroidering a small accent, like a tiny bird or a single decorative flower that is smaller and less demanding than the main shapes. This gives you a quick burst of creative variation and lets you feel like you're completing a finished piece, even if it's small, before jumping back into the main structure. It prevents the entire project from feeling like a single, unending chore.
Remember that perfection isn't neccesary for every square of thread. Sometimes a slightly less perfect stitch is fine if it lets you maintain your momentum and keep moving toward the finish.