These thoughts are based on the tour experience, but some of them can be generalized to all life experiences.
You can do more than you think you can, but you have to try.
Know your limitations but don't be afraid to try going outside them, just choose the when/where/why wisely.
Accept the trip you are on - don't try to make it what you expected or wanted it to be.
Realize that everyone on your tour is on a different tour from everyone else on your tour. Each person has their own expectations, needs, problems and goals and they may not match yours.
PACK LIGHT. Then take out at least one third of what you packed. Honestly, no one cares that you only have two t-shirts. Unless you go off on your own, there will be no restaurant or venue that won't let you in wearing shorts and a t-shirt - or bike shorts and jersey for that matter. You and your tour mates will be hauling those bags in and out of the trailer and up and down stairs for two solid months, they seem heavier every day.
Be open to new experiences, new people and new foods - but hold on to the things that make you comfortable and happy.
Take pictures and keep a journal/blog - it is amazing how quickly the towns/states/hotels and rides start to blur together in your memory.
Do it. Do it NOW - tomorrow might be too late.