I find myself in a delicate situation.

I applied for a job (higher position for the same employer) which I was pretty confident I would get, but management decided to give the job to someone older, that had "more experience" (although I know darn well that they know I could have done the job).

To make a long story short, my boss is expecting me to train this new person. To tell them more about the business, our current project, etc.

I am obviously upset after not landing this promotion, and I am confused in regards to how I should behave at this point. Shut up and be collaborative, and wait for the next opportunity? Tell my boss I "can't do it"?

Just trying to get some input... thanks.