My dog isn't invited anymore

I've been taking our dog, Sam, on my morning runs with me. Since it's still dark out, it was nice for a sense of added protection, plus he loves going on walks. Today was the final straw, however. I'd get annoyed with him in the past because he'd want to stop and sniff stuff. I can't fault him for that--he's a dog and dogs like to sniff things. I'd just yank the leash and he'd catch up with me. Monday I was pretty impressed with him because he'd get as far ahead of me as he could, sniff, and then fall back in line with me once I got to where he was. Not so much today.

He tried to take off after a cat at one point. Then a bunny. Then there was a guy running with his dog, and Sam freaked out and wanted to meet that other dog. He's usually really calm when he sees other dogs, so I was surprised with how he was acting today. When we saw the other guy I had to stop running, let them get far enough in front of us that the dog wasn't a distraction and then keep going. Ugh. I didn't want to get up and go running this morning anyway, so having to stop during one of my running segments did not help.

Poor Sammy doesn't know it, but he's not coming with me anymore. I had figured I wouldn't take him much longer anyway because the length of the runs is increasing (Friday I do 20 minutes of straight running...God help me!), and I didn't want him to have to run the whole time. But he pretty much decided for me today that taking him with me just isn't going to work anymore.