When I am tired and I slip into bad form when I am walking I do this again. I have to remind myself to relax because I'm almost always stiff.
Also when I am using bad form and running I will limp, favoring my right hip and putting stress on my left. I had a hip injury and sometimes I will favor it even when it's not really acting up.
Something I do to combat both situations is watch my shadow. I run in the early morning so the street lights are still on. It's not exactly a mirror, but it does show me things I am doing and I can correct.
tonight it made a difference. I was stiff from my squats and I kept slipping into bad form. If I kept running badly I would just end up in more pain.
So I watch my shadow self and make corrections. Little things that can make all the difference.