It means you are ready to take your act on the road, or that you are ready for prime time, or that you know what you are doing and where you are going. You are (not meaning to be sexist) “A man with a plan who is knowing where he’s going.”
In other words, what everyone else above me has said. You know where your keys, glasses and cell phone are (and the latter is fully charged), you aren’t crying or otherwise upset, your gas tank is full, you have exact change for the bus, you remember what you have to do and where you have to be and when you have to be there, your projects are completed on time, your bills are paid, your clothes are clean (and your socks match each other), you smell good, you ate breakfast, you took your meds, and all is right in your world.