For me, this means that a) I am not interested in my work, b) I am tired, or c) I am burnt out. All of these can be greatly helped by getting some good sleep, a

For me, this means that a) I am not interested in my work, b) I am tired, or c) I am burnt out. All of these can be greatly helped by getting some good sleep, and a + c can be helped by having some fun - especially social or physical activity somewhere new (weekend trip, drinks with friends, etc). You can try and force yourself to focus with tools and mental tricks, but that always seems to make me feel worse. Better to get at the root cause, which is almost always stress or physical exhaustion.