There are folks that feel if they don't make a final table then they actually lost whatever toun they're playing and that's the feeling you should develop by gaining more knowledge and experience with whatever game/tourn you're playing. And that's the mindset you should have or at least should be working on obtaining if you want to get good at them.
That feeling only comes when you have a vast knowledge of whatever game you're playing, the experience to ACCURATELY judge your opponents and understand tourn structure and to back it up with enough results as proof that you actually know what you're doing.
This stuff about being nervous at a final table
tells me that there's a good chance these folks are playing over their heads either competition wise or for some reason these folks sound like they're surprised to get to a final table as if they don't belong there, lol which is silly.
If folks get that feeling then I would suggest better tourn selection to where you can reach whatever goal you're setting for yourself like cashing a certain percentage, coming in the top 30% of a tourn so many times, making the final table or whatever goal you set and be able to do it a lot and have the confidence backed by results to show you can do it.
Or you're going to be dead money and unless you're just playing for fun then more than likely you shouldn't be playing those tourns because they're over your experience level for some reason.
You should find ways to get over that feeling. One uber simple way would be to play more multi table Sit in Gos at are at your level to increase you
odds of getting to a final table so its not such a new experience or feel like a big deal when you play tourns. But again, you should work on making it so getting to the final table is the norm rather than an exception so you won't be nervous any longer.
GL