We need to do a crash course of something that I think will help you -relaxation and visualization. When you feel that sense of dread kicking in, stop, and change your thoughts to something else, something pleasant. Tune in to the "Movies Of Your Mind". Let's figure out what that will be. Where is your favorite place to be? What about your favorite vacation spot? I will use mine as an example. When I learned this myself, I chose the top deck of Disney Wonder.
How to do it? Find a quiet spot where you will not be interrupted. Turn off the phone. Light a candle if you like that, or put on some soft music or nature sounds, preferably appropriate to wherever you're going.

Start to relax your body physically. Breathe deeply, from your abdomen, not your chest. Slowly in through nose, slowly out through mouth. Again and again. Visualize your muscles relaxing beginning at the top of your head and going down - neck, shoulders, chest, arms, belly, legs, feet. Don't rush, take your time. Do this for several minutes. Picture each muscle individually relaxing. Don't allow your mind to wander; stay focused on your muscles.
Once your muscles are relaxed, in your mind, put yourself in your favorite place. Visualize yourself doing what your favorite thing to do would be. Kick in your senses: hear the sounds; smell the aromas; feel the air; see the sights; enjoy the pleasure you have being here. Stay there for a while and take it all in. Continue to feel how relaxed your muscles are. If you're a spiritual person, thank God and your guardian angels for bringing you this joy today. You are in control here. Leave when you're ready to leave, but promise you'll be back soon for another visit.
Research has shown that doing this daily helps kick in the relaxation respose for the rest of the day, even when things get stressful. The beauty of it when you get good at it is that you can make it kick in anytime, anywhere. It becomes your Happy Place. And it is extremely effective. Try to make time today to try it out, even print it up and take it away with you so you can enjoy your trip.
Other visualizations that might help you are picturing yourself walking arm and arm with us, a strong force of survivors and friends who care, together. A favorite of the people who taught me this was to picture yourself as a big, strong tree with roots that go into the ground for "grounding". You can put yourself anywhere you want and visualize yourself being very strong. Practice and do it in place of the visceral reaction you're having to stress and worry, please. I guarantee you it will be much more pleasant.
Wabt a report back later on how it went, ok?