Don't lie, but don't embellish. When asked have you smoked pot, the answer is "yes." When asked how often, the answer is "one time only." Those are true answers, and will display to the questioner your drug use was not habitual, but a one-time "recreational use" mistake. I wouldn't pile on a bunch of extra info (i.e. the whole anxiety thing) unless they specifically ask you about that stuff. Don't offer up additional info until it's directly asked for. After that, all you can do is hope for the best. If you lie, they will find out and you will almost certainly lose any chance you did have at flying jets.