Just thought I'd talk about something that happened to me Sunday before last... I was asked to play a hymn in priesthood meeting, and the hymn was in the key of A major (three sharps).
For some reasons, hymns tend to have flats more often than sharps, so I'm more accustomed to playing in keys which have one or more flats. And three sharps was quite a bit to watch out for.
So I simply transposed it to A flat major (four flats)—I found that rather easier to play. And the good part is that I could just pretend it was written in A flat major all along since the notes would be on the same lines and only the key signature would be different, so I could play straight from the sheet music without having to think too much :) I only had to convert one note in my head; IIRC, it was an F natural which became an E, or something like that.