Susie and Susan: I do hope your worst fears are unfounded and that you get to go on your planned holidays. However, I think an incident like this can wake you up to the fact that one day your marriage will end in the death of one spouse, and that is most often the wife.
My husband and I were married for 46 years before he died of prostate cancer. We were close and loving, and particularly enjoyed travel and holidays together, but we had always pursued separate, as well as joint, leisure interests and had some separate friends - we didn't always socialise as a couple or rely entirely on each other. We felt that this helped to keep our relationship healthy, and hadn't really thought of it as "future-proofing" against bereavement, but during my husband's terminal illness, he kept encouraging me to maintain and develop my interests and my independent social life.
After he died, I came to realise how wise this approach had been. I still had my friends and my interests, and more importantly, the confidence and resilience needed to go out there and get on with my life. It isn't easy learning to be a widow and do everything on your own, but I think it would have been much harder for me if we had always lived in each other's pockets and done nothing independently.
You can't spend every day anticipating widowhood, but you can perhaps develop some independent interests and activities that don't rely on your husband. This can be fulfilling and rewarding, and may help make you less afraid of facing a lonely old age.