Some time ago i discovered, that when I am unable to write code, I am still able to engage in less demanding but still very beneficial activity for my project:

Some time ago i discovered, that when I am unable to write code, I am still able to engage in less demanding but still very beneficial activity for my project: Pair programming with less experienced members of the team. It was very important for me, because previously, when i had "bad day" i was ending with completely wasted day. Now, even when i am not able to do work myself i am still able to boost significantly someones output. For solo projects, watching advanced tutorials, or conference talks about technology beneficial for current project gives me sense of progress during days when i am unable to code.