Worrying is the interest paid on a debt that you may never owe.
After taking cognitive behavioural therapy, it really helped me to stop worrying. Preparation and organisation is a good way to combat excessive worrying.
I don't see anything wrong with the steps he/she has taken to be prepared for the next day. I don't think it should be enough to keep you up at night, but if you feel better about yourself having prepared before bed, simply make that a part of your pre-bed routine.
The other worries are indeed needless ... I'm an introvert so I'm naturally more withdrawn from my peers/colleagues/etc, but I could care less about what people think of my hair/clothes/etc. If you're clean, somewhat groomed and not wearing outlandish clothes, you'll simply blend in and no one will consider those "externals".
As an aside, people who know you probably would look past the externals anyway.
“Worry is like a rocking chair: it gives you something to do but never gets you anywhere”
― Erma Bombeck [Also - Van Wilder - Party Liason]