My dog has bucked up & quit walking on me on our past three walks. Usually, she is an eager beaver & I have to make her stop. Otherwise she seems fine. She's been eating good, sleeping good, drinking, no vomit, regular stool. She'll do a few laps, then just stop like she is ready to go. She won't go forward, but she eagerly goes toward the house. I thought it may be because she was hot, so I walked her after the sun went down. Same thing. What's up w/ that? Should I try to push her, or let her tell me when she's tired?