I've done perhaps 3 or 4 longish trips since getting the license 8 months ago, so I consider myself equally lacking in real experience. For what it's worth, theat nagging feeling of having forgotten somthing never quite goes away (not in the first 100hrs, anyway). I'm always really nervous the morning of a flight, even just a local jolly with my daughter.
My first real "trip" was to Duxford 3 months after license issue and I spent literally weeks worrying about it - at one point I'd even convinced myself to take a safety pilot - just in case. In the end I went alone and it all went exactly to plan and was a huge confidence builder as well as been a very enjoyable day.
What's my point? I guess I'd say it's natural and very healthy to be a little apprehensive before what is obviously a milestone trip. If you were going into it with a flippant over-confidence, then that WOULD be a problem. Plan, check, check again, then relax and enjoy.