You get the clippers out and your dog leaves the room. Or they let you start, then twist, pull away and mouth your hand.
Safety note
Pain frequently presents as a change in behaviour rather than as obvious lameness. If handling a paw, an ear or a leg has newly become difficult, book a veterinary examination before you train anything. Get help now if your dog has growled, snapped or bitten during grooming.
Why this gets worse with practice
Every session your dog struggled through taught them that the clippers are worth avoiding. Restraint makes that lesson stronger, not weaker.
Punishment-based approaches are associated with fear, avoidance and defensive aggression. Holding a frightened dog still to get the job done sits in that territory.
Reward-based methods are what is recommended for training and behaviour change. Grooming is training, and it follows the same rules as everything else.
Rebuild it in 30 second sets
Working below the threshold at which your dog reacts is the condition for learning. If they pull away, the last step was too big.
Put the clippers on the floor, feed your dog, and put them away again. 30 seconds, twice a day, for 3 days.
Touch 1 paw, feed, and let go before your dog moves. Do 5 reps, then stop.
Hold the paw for 2 seconds, feed, release. Build to 5 seconds across a week.
Touch the clippers to 1 nail without cutting, feed, and stop. Spend several days here before you cut anything.
Cut 1 nail, feed, and end the session. One nail a day gets you through a paw in a week.
Let your dog leave
Give your dog the option to walk away, and stop when they take it. A dog who knows they can leave usually stays longer next time.
Work with your dog standing or lying by choice, not held in your lap or between your knees.
Spread food on a plate or a mat for the same 30 seconds, so there is something better to do.
Stop at your planned end point rather than when your dog protests, so quiet is what ends the session.
Write down what you did each day, so slow progress is still visible progress.
In the meantime
Ask your veterinary practice, or a groomer who works with reward-based handling, to do the overdue nails while you rebuild.
Try a file or a grinder if the clipper itself is the problem, introduced the same slow way.
Practise ears, collar and harness handling in the same 30 second sets, so grooming is not the only handling your dog knows.
Safety note
See your veterinarian if a nail is cracked or bleeding, if nails are long enough to touch the floor, or if your dog is limping. Do not force a struggling dog to finish. If grooming is producing growling or snapping, stop and get help now from your veterinarian and a qualified behaviour professional.
Today's version, in one line: clippers on the floor, feed, put them away. 30 seconds, and nothing else today.