Hi pega,
I took the Test last Friday and now I am waiting for my results. However, I understand you because sometimes I felt nervious because of the time
But the clue in this kind of Tests is to stay calm... Otherwise, we are not going to be able to concentrate and reflect our English knowledge... And that is the goal of TOEFL iBT... To show that you have an advanced level of English
I think that it is a good practice to relax at least one day before the Test. In my case, I went to the movies to watch a comedy and then I ate a pizza with red wine... For me, red wine is useful because it helps me to relax and to sleep deeply at night... Also, I really like red wine
Then, early in the morning I drunk some orange juice and went to the Test Center. In the break, I ate some chocolate because it helps your brain to work better. Finally, I breath deeply when I felt nervous and try to focuss all my atention on each question...
I hope these tips would help you. Be confident... TOEFL iBT is only a Test and you can do it
Good Luck!!!
Cheers.