Have you ever been forced to do a job in which you weren't proficient? How did you cope?

My current job was essentially chosen for me with no regard for my knowledge or personal interests. I have to do the job regardless even though I’m not proficient in it at all. To top that off, I am supposed to be supervising co-workers at this job. Has this ever happened to you? How did you cope? Becoming proficient in it has proven to be a daunting task.