I don't worry about the model kit or the paint. Both of those can be replaced if I mess something up, and all the parts that go on after the decals and gloss coats can still be useful in the spares box.
I do get just a bit nervous about the first few decals, though. Should I have coated the decal sheet, instead of deciding that the decals were new enough? Will the coating that I put on that old sheet really be okay, or will it still shatter? Heck, for some sheets, it is a question if the decals will come off the backing paper or not. Plastic I can replace, paint I can get more of,,,,,,,,but, decals can be very hard to find and replace. I still have a small list of decals that would make things easier for me, but, they were in kits that went OOP a long time ago, so I probably won't find them. If I do, I know I will only get one good chance to use them, without any chance of finding a second set.
But, there is nothing to do for it except to charge ahead and see what comes out of the effort. I am not building in numerical order anyway, and probably won't finish the set in my lifetime.
Rex