The short answer
After being passed over, find out which gap you are facing: an evidence gap, a criteria gap, a sponsorship gap, or a structural one. Each has a different response, and guessing wrong wastes months.
The first hours after a promotion decision are the worst time to draw conclusions, because doubt will offer you one immediately: you were not good enough. That is a story, not a finding. What you have is a single data point and, usually, a short explanation that was optimised for being said out loud rather than being useful.
Four gaps can sit behind the same outcome, and it is worth checking each one. An evidence gap: your work is real but no one can point to a verifiable record of it. A criteria gap: the bar for the level was never written down, or you were measured against an unstated version of it. A sponsorship gap: nobody with standing in the room argued for you. And a structural gap: the decision reflected who is comfortable to promote in that environment, not what you delivered.
These need different responses. An evidence gap is answered with documentation. A criteria gap is answered with a direct question. A sponsorship gap is answered with relationships built well before the next cycle. A structural gap is answered with a decision about where you invest the next two years — and that is a legitimate strategic answer, not giving up.
So the goal of the next two weeks is diagnosis, not repair. You are gathering information about which gap you are in. Everything else — the conversation, the plan, the decision about staying — gets easier once that is named.