I've noticed that the journals I like reading over all tend to be very short and very pithy, where I only record what is interesting. And that's usually about what people said or did and what surprised or delighted me, rather than details about planning.
Whenever I sit down to write a journal entry I always want to basically map out my entire day and what I did and when I did it, but unless you are making a wedding planner notebook, you won't care that you had to go to three appointments and one was canceled and so forth. You will care that the flower girl said something cute and the taxi driver was very supportive of chocolate cake over carrot cake and that your uncle promised he would swim if they couldn't get a flight.
I guess what I'm saying is that little anecdotes are what you'll want to remember, not the price of everything or how stressed out you are. And making note of these little anecdotes as they happen might encourage you to be less stressed.