toffeecushion, the only example I can give you is that of my sister, she has always suffered from anxiety and depression, quite a few years ago she was prescribed norethisterone (this was for too much bleeding) when she told me I immediately though that it would effects her moods and was surprised when she reported that and said she got on well with it.
Another case of us all being different
You could delay taking it until after your holiday, or take it and if it causes your mood to plummet just stop, its either one or the other and only you can decide.
If it were me I would be inclined to follow the doctors advice, then at least you could say I gave it a go.