I distinctly remember an incident years ago. I was in the middle of my then normal workout and -
bang - my body and mind shut down. I stopped right in the middle of what I was doing and could not restart. That was near the time my depression became unmanageable.
By the way, I'm glad you kept walking. If you can't run, walk.
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My dog

mastered the "fetch" command. He would communicate he wanted something, and I would fetch it.