We have two situations that the following sentences can be used in:
- Keep your head up.
- Keep your chin up.
- Keep your pecker up.
a. When you want someone to be hopeful again after a setback.
b. When for instance a soccer player keeps head down when he is playing and his / her coach wants to ask him / her to keep head up when he is playing, (or in similar situations.)
To me, these three sentences mean the same thing and the only point that should be considered is that the last one sounds too informal (maybe impolite)
I wonder which sentence is used for which one of the two cases that I wrote above. (I think all three sentences have both of the usages.)