Here's the stick - what's the problem?

I always find it difficult to blip Dimairt whilst trying to throw sticks at the same time. It rarely works - either he is too fast for me, or I shoogle the camera, or the camera gets wet from wet dog!
So, I blipped him after he had returned with the stick. While I was trying to focus, he kept picking up the stick and putting it closer to me - finally putting it on my foot. I mean, how blind am I?
He never seems to tire running and fetching and splashing into the river; but I noticed today that he was having a wee bit more of a problem climbing out of the river. (He's 9 now, and has had a hip operation 2 years ago.)
I decided to rest him on the road home, and not throw the stick. He couldn't understand this, and kept trying to snatch it out of my hand. He then proceeded to run off and bring me other sticks - he must have figured that I wasn't happy with the one in my hand.
How can you possibly say "It's for your own good" in dog language?