No one wants to get sick while on holiday; not only can it ruin your trip, it could be potentially expensive as well. There are a couple things you can do before your holiday to ensure a healthful trip.
First, check with your health insurance provider to find out what, if anything, will be covered if something should go wrong. If you are traveling to a particularly dangerous place, or plan to participate in some potentially injuring activities, make sure your insurance covers you if the unexpected happens. Also, pay a visit to your doctor. You should do this anyway, but making sure you are in tip-top shape before you head off will hopefully mean you'll stay in good health. Your doctor should also be aware of any health travel warnings that may be in effect for your destination, as well as be able to recommend any vaccinations.
Luckily, if you are planning a trip to Europe, you should be safe from any "exotic" diseases you could catch in other countries. But don't forget simple things like allergies. If you are plagued with a runny nose and watery eyes every time something starts to bloom around you, check to see what may be sprouting while you are in town. And then pack medications accordingly. Also research the safety of the water, and if there have been any outbreaks of disease recently.
The Travel Clinic is a UK based doctor's office specializing in pre-travel health needs. They offer both health and travel alerts on items of interest going on around the world. Travel Health is another UK based site and if you are looking to see what may be happening health-wise in your vacation destination, visit the World Health Organization.