The old dog's teeth had been ground down by constant use.

Djokovic broke twice in each of the opening two sets, dismantling 6ft 8in Anderson's service game and grinding him down in the rallies.

I'm living in a world where I don't really fit
Every day walking through the same old shit
I'm gonna get my gun, gonna get prepared
I'm not impressed and I'm not scared
Don't let the bastards grind you down!
Don't let them grind you down!
Don't let the bastards grind you down!
Don't let them grind you down!

Grind down

Meaning

Verb