TELL HIM!!!
Mine is aware immediately I begin to go under and from experience we know how I might be.
So I have anti-anxiety medication, i.e. a 'valium'-type pill. Knowing that I have it with me helps. Knowing that it helps within 20 mins. helps.
Explain that you are worried about spoiling it for him. Depending on the type of holiday, is there something that he can do if you decide to stay behind? Museums etc. so that at least he gets out and about, DH goes fishing or we drive to a quiet spot and simply sit. For years I had guilt about the potential to spoil things but now it's a bonus if I get to the holiday
and anything after is great.
Don't beat yourself up. Make sure that any paper work you have is close by and that you have copies at home. Pack early so that you don't back yourself into a corner. My clothes are laid out ready days ahead and cases close by. I put everything in at least 2 days prior to travelling ;-)
R U going somewhere nice?