Confidence....If you can do it on tumble trac, then you can do it on floor.
Ask for a spot ..... try and find a mental place where you feel comfortable doing it....
Imagine yourself doing it without a spot.....focus on one thing, straight arms or hands pointing in etc....
If you focus on 'I have to do it or else'....It becomes too much...
Think...'Maybe I will go for it this time' .
Remember that the fear is temporary.....it will go away and you WILL be able to do it.