I'm sorry you feel like this. I'm an anxious traveller who has to travel too much! I really get it. My anxiety builds as the trip gets nearer and the last week before is pretty bad. I would honestly be happy to stay at home for the rest of my life! Part of my anxiety is from being in pain when sitting, which is pretty hard to avoid when travelling!
I think the key is to break things down. Sorry if this is really obvious.
What are you most anxious about? If it is the things to do, make a list! Then prioritise it and plan to do, say, 3 things a day (if you have time of course). Write out the days with their allocated tasks. I find it less overwhelming that way.
If you are anxious about the actual traveling, trial some herbal calming tablets or ask you doctor about diazepam. If you hate flying, and the flight is four hours, get through it 15 mins at a time.
Lists, lists, list for packing! And if disorganised like me, separate lists for toiletries/makeup, medication, etc
Take some familiar things and plan some travel treats - new mini toiletries, a book, magazines, etc
If I am dreading a whole trip, I try to focus a few particular things I'm especially looking forward to doing.